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In nova fert animus mutatas dicere formas 
Corpora. . .- Ovid. 



T O 










i ffi i i. i "i i" i -M.L. I - ..■■ u,.m iw!j»»i»i»g»pi<>TWWw» L>i. i Mj ju a— — ^^ 

t H E 

E F A 

AFTER the intimation given in t|i@ 
preface to my third volume of Ob^ 
fervations on different kinds of jiir^ 
publifhed about V^o years ago, vi^? ** that 
*^ I {hould certainly give myfelf and my 
** readers fome refpite ; forefeeing that my 
♦* attention would be fufjiciently '^xig^g^^ 
^^ by fpeculations of a very different na-^ 
^^ ture 3" fome apology may be exp?£ted 
for obtruding on the public another vglum§ 
of experiments, and efpecialjy fo large a 0|j@ 
as that v^hich is now before them, 

In tjiis cafe, however, it may be fufficlanl 
to alledge the inftability of human purpoftg 
and purfuits. But the fpeculations rgferr^i 
to, which were of a metaphyfical nature^ did 

A 3 m% 

vi The PREFACE. 

not happen to engage fo much of my atten- 
tion as I expeded, and did not, at any time, 
much interfere with my philofophical pur- 
fuits. It is alfo to be obferved, that that 
kind of writing is a thing of a very different 
nature from this. I can truly fay (nor will 
it be thought extraordinary by thofe who 
confider the nature of thefe fubjeds) that 
iingle fedions in this work have cofl mc 
ji^ore than whole volumes of the other j fo 
great is the difference between writing from 
the head only, and writing, as it may be 
called, from the hands. To the former 
.little or nothing is requifite but calm re- 
jfleilion ', whereas to the latter much labour y 
^nd patience, and confequently much timet 
as well as expence^ are neceilary. 

' I have, belides, been engaged farther than 
I exped:ed in philofophical ftudies by the 
■profecution of fome inquiries which I had 
left unfinifhed before, and efpecially by the 
repetition of procefles the refults of which 
liad been quellioned by others. Various 
other circumftances, of which mention is 
made m the courfe of the v/ork, likewife 


The preface. vii 

contributed to lead me ftill farther in the 
fame path. And having acquired a fond- 
nefs for experiments, even flighter induce- 
ments than I have had would have been 
fufficient to determine my conduct. 

But in this I v^ould by no means be under- 
ftood to be making an apology for what I 
have done. I am far from confidering the 
bufinefs of philofophy as a thing that is 
cenfureable, or requiring any apology. On 
the contrary, though I do not confider 
thefe ftudies as the fir ft in rank and value, 
I think their importance is generally much 
under-rated; and I earneftly wifh that 
more attention was given to them by 
thofe who have ability, leifure, and the 
neceflary means for profecuting them. For 
it muft be acknowledged that in thefe 
ftudies mere genius can do nothing without 
the aid of v/ealth. Indeed, f peculation^ 
without experiment^ has always been the 
bane of true philofophy. 

I am forry to have occaiion to obferve, 

that natural fcience is very little, if at all, 

A 4 the 

viii _ The preface. 
the objedl of education in this country, in 
which many individuals have diftinguifhed 
themselves fo much by their application to it. 
And yet fcientifical purfuits have fuch an ad-* 
vantage over moft others, as ought more efpe^ 
cially to recommend them to perfons of rank 
and fortune* They never fail to furnifh mate^ 
rials for the mofl agreeable and ad;ive pur-- 
fujts, and fuch as are, at the fame time, ih 
the higheft degree, ufeful and honourable, 
and are, by this means, capable of doing 
unfpeakably more for them than the largeft 
fortunes can do without this refoUrce,Were 
perfons thus engaged, there would be lefs 
temptation to have recourfe to pleafure and 
djffipation, for the employment of their 
vacant timcj and fuch purfuits would be 
particularly valuable to thofe who have no 
talent for politics, or any proper call, to 
gccupy themfelves in public affairs. Belides, 
the laft is a path in which, from the nature 
of things, only a very few can walk j and 
the former, "j/s, a courfe of vicious pleafure, 
it is much to be laiiiented that any huii>an 
t)eing (hould tread, 


The preface. i« 

Man is a being endued by his creator with 
excellent faculties, and not to have ferious 
objeSis of furfuit is to debafe and degrade 
himfelf. It is to rank himfelf with beings 
of a lower order, aiming at nothing that is 
much higher than the low pleafures they arc 
capable of; at the fame time that, from 
the remains of nobler powers, of which h« 
cannot wholly divefl himfelf, he is incapable 
of that unallayed enjoyment of fenfual 
pleafures that brutes have. 

I Ihall not repeat, in this place, what I 
have advanced in favour of fcientifical pur- 
fuits, as peculiarly proper for perfons of 
large fortunes, in the preface to my Hijlory of 
EleBricifyf and my late Obfervations on Edu- 
cation ; but would obferve that, if we wifl? 
to lay a good foundation for a philofophical 
tafte, and philofophical purfuits, perfonis 
fhould be accuflomed to the fight of expe- 
riments, and procelTes, in early life. They 
fhould, more efpecially, be early initiated- 
in the theory and pradtice Q)i invejligation; 
by which many of the old difcoveries may 


X The preface. 

be made to be really their own 'y on which 
account they will be much more valued by 
them. And, in a great variety of articles, 
very young perfons may be mad^' ib faf 
acquainted with every thing necelTary tp be 
previoully known, as to engage (which they 
will do with peculiar alacrity) in purfuits 
truly original. 

At all events, however, the curiofity and 
furprize of young perfons fhould be excited 
as foon as poffible -, nor fhould it be much 
regarded whether they properly underftand 
what they fee, or not. It is enough, at the 
firft, if flriking fadts make an impreffion on 
the mind, and be remembered. We are, at 
all ages, but too much in hafte to underftand, 
as we think, the appearances tliat prefent 
themfelves to us. If we could content our- 
felves with the bare knowledge of n^w faBsy 
and fufpend our judgment with refped: to 
their caufes, till, by their analogy, we were, 
led to the difcovery of more fad:s, of a 
fimilar fiatuce, we fhould be in a much 


The preface. tl 

Airer way to the attainment of real know* 

I do not pretend to be perfe<flly innocent 
in this refped: myfelf ; but I think I have aa 
little to reproach myfelf with on this head 
as moft of my brethren 5 and whenever I 
have drawn general conclulions too foon, I 
have been very ready to abandon them, as 
all my publications, and this volume in par- 
ticular, will evidence. I have alfo repeatedly 
cautioned my readers, and I cannot too much 
inculcate the caution, that they are to con- 
lider nQwJa^s only as difcoveries, and mere 
deduBions from thofe fa6ts, as of no kind of 
authority j but to draw all conekifions, and 
form all hypothefes, for themfelves. 

Having now begun a new work, it may 
perhaps be expected, by thofe who are 
pleafed to think favourably of my paft 
labours, that I fhould proceed with the fame 
fuccefs. But nothing can be more uncertain 
than this. I before compared philofophizing^ 
to. huntings and though hitherto I have^ 


xii The PREFACE. 

been pretty fortunate, I may hereafter 
follow the chafe to very little purpofe. All 
I can fay is, that I ihall think myfelf happy 
to have leifure, and the means of profecuting 
thefe inquiries ; and that I fhall certainly, 
by fome chanel or other, account to the 
public, in proper time, for v^hatever fuc», 
cefs I may meet v^ith. 

I fhall conclude this preface v^ith ob- 
ferving, that the Abbe Fontana having 
heard that I had found pure air in water, 
was fo obliging as to fend me an account of 
fome experiments of his, made at Paris, 
above a year ago, in confirmation of the 
fame thing. He extracted by heat pretty 
pure air from feveral kinds of water, but 
efpecially diftilled watery though far fhort 
of the purity of that which I procured in 
the circurnftances mentioned fe6t. xxxiii. 
One meafure of the beft that he procured, 
mixed with two meafures of nitrous air, 
occupied thefpace of 2.5 meafures ; whereas 
the fame meafures with mine, as will be 


The preface. xiii 

feen, occupied the fpace of little more than 
half a meafure. He alfo does not mention 
his having obferved the difference in the 
quality of air extradted-from water in con- 
fequence of expofure to the air, or the fun, 

London, March i, 1779.* 




'TJoe Freface ^ - V 

, T^he IntroduBion^ - ■ • . .-j ■ xxv 

, ^e(3:ion I. Obfervatiojts relating to the 
NiT^Rous Acm, afid efpecially the Cqlou.r 



^^^.11. Of the Nitrous Acid Vapour 26 

Sedt. III. So?ne Fhenomena attending the 
Solution of Metals in Nitrous Acid 30 

Sed:. IV. Of the Changes to which Ni- 
trous Air is fiibjeSi ■ — ■ " - ^r 

Se(ft. V. Of the Impregnation of Water 
,with the Vapour of Nitrous Acid 6 c 

Sed. VI. Atte?npts to preferve animal 
^ubjiances in nitrous Air — 60 

Sed:. VII. 


Scd:. VIL Mifcellaneous Experiments rC" 
lafing to nitrous Air — jp 

Sed:. VIII. Of the Colour of the Marine 
Add — .— . — -7§ 

$e€t. IX. Of the Impregnation of Marine 
Acid with various earthy Subjiances 87 

Se6t. X. Of theEffeB of a continued Heat 
en Spirit of Salt in Glafs Tubes hermetically 
fea-led " — ■ — - — 92 

Sed:. XL Of the Expofure of various Sub- 
dances containing Spirit of Salt to a continued 
Heat — _ 103 

Seft. XI I. Experiments relating to the 
lyif charge of the Colour of various Solutions 
made by the Marine Acid — 108 

Scd:. XIII. Of the Vitriolic Acid 1 16 

Sed. XIV. Of the volatile Vitriolic Acid, 
and Vitriolic Acid Air — 122 

Sedt. XV. Of the Phofphoric Acid 133 

Se^. XVI. Obfervations relating to the 
black Powder produced by the Agitation of 
impure §uickflver — ■ — 141 

Sea. XVII. 

The contents. 

Sedl. XVII. Of the Agitation of pure 
Mercury in Water — — 159 

Seft. XVIII. Of the Effe5i of long con- 
tinued Agitation on ^ickjilver 184 

Sed. XIX. Of the Conftitution of dephlo- 
gijiicated Air, and a Review of the Obfer- 
vations relating to it — ■ — 192 

Se(ft. XX, Of the "ExtraBion of dephlo- 
gijiicated Air from feveral Mineral Sub- 
fiances — — 203 

Se6t. XXI. Of the ProduBion of dephlo- 
gijiicated Air frofn the Vitriolic Acid and 
Iron — — 213 

Secft. XXII. Of the Frodudlion of dephlo- 
gijlicated Air by Means of the Vitriolic Acid, 
from other Metals -—* — 226 

Sed. XXIII. Of the ProduBion of de- 
phlogifiicated Air from Earthy Sub- 
stances by Means of the Vitriolic Acid 236 

Se6t. XXIV. Atfefnpts to procure Air 
fro?n 'various Subjiances by tneans of Spirit of 
Salt — -— — 240 

a . Sea:. XXV. 

The contents. 

Sedl, XXV. Mifcellaneous Experiments 
relating to Dephlogtfticated Air — 245 

1. Hhe very great Diminution of dephlo- 
gijlicated Air by Nitrous Air - — ibid. 

2. Of procuring dephlogijiicated Air hy 
means of crude Nitre — 249 

3. Of the rufting of Metals in Air . 253 

4. Of the Detonation of Nitre 354, 

Sea. XXVI. Of the Prefence ^ Earth 
in atfnofpherical Air, or in dephlogijiicated 
Air, as the proper Origin and B a/is of it 260 

Se(5t. XXVII. Various Ohfervations relat- 
ing to the Diminution of common Air 269 

1 . Of the Purify of Air in different Cir- 
cumftances — — ibid. 

2. Of the State of the Air in Hot- 
houses. -^ — 247 

3. Of the EffeSl of the ViE.^s^i'^ AT lou 
of the Body on Air —— 275 

4. Of the State of the Air /;z D i n i n g - 
Rooms — - — 278 

5- Of 

The contents. 

^. Of the Eff'e5t of St ^ AM on Air 281 

6. Of the EffeB of the Electric 
Spark on common Air — 284 

7. Of the EffeB of the Cakes of Copper 
and Iron on Air — . 288 

8. Air injured by the Effluvium of 
Water frefi diflilled ■ 293 

Sedt. XXVIII. Obfervations relating to 
the Melioration of Air by the Growth 
OF Plants — — 296 

Sed:. XXIX. Of the State of Air confned 
in the Bladders of Sea Weed — 313 

Sedt. XXX. Of the Property of the Willow 
Plant to abforb Air — — 320 

Sedt. XXXI. Of the Growth of Plants 
in dephlogifticated Air, compared with their 
Growth in other Kinds of Air — 326 

Sedl. XXXII. Of the Growth of Plants 
with their Leaves in fixed Air, ajjd their 
Roots in Water impregnated with fixed 
Air — - • — — ' 329 

a 2 Sedl. XXXIII. 

The contents. 

Sedt. XXXIII. Of the fpontaneous Emijion 
of dephlogifticated Air from Water in certain 
Circumjiances — — 335; 

Sedt. XXXIV. Of Inflammable Air 360 

1 . Of the ProduBian of Inflammable Air 
from Iron and a Solution of Galls 36a 

2. Infla?nmable Air from Oil of I'ur- 
pentine — — 36^5 

3. Whether there be any Acid in Inflam- 
mable Air -— — 364 

4. hflammable Air not affeSted by the 
^leBric Spark — - — 367 

5. Inflanunable Air decompofed by Heat^ 
in Tubes of Flint Glafs — 368' 

5. Inflammable Air diminijhed by Char- 
foal — 37S 

6. JVh ether inflammable or nitrous Air 
Gontain more Phlogijion — • ibidv 

Sedl. XXXV. Of Fixed Air — 384 

r. Of the Ge?ier at ion of Fixed Air from 
the Vitriolic Acid ■ ibid.. 

2. Of 

The contents. 

2 . Of Fixed Air imbibed fro?n the At- 
mofphere - - . 388 

3 . Attej7ipts to extraB fixed Air frojii 
various Siibjiances - - 396 

4. Fixed Air expofed to Heat 398 

5. Air fir om Charcoal and Precipitate 
per fie - - ibid. 

Sed:. XXXVI. Fxperiments on Cream ofi 
'Tartar — — 401 

Sea. XXXVII. Mificellaneous Obfierva- 
tions on Subftances expofied to a long cofitinued 
Heat — - — — 406 

Seft. XXXVIII. Fxperiments in EleSiri* 
city — — — 425 

Sedl. XXXIX. Miscellaneous Expe- 
riments — — 429 

1 . Ofi the Colour ofi Minium ibid 

2. Ofi the Mixture ofi Vitriolic Acid 
Air, and Fluor Acid Air. 432 

a 3 3- y 

The C O N T E NT S. 

3. Of Fluor Acid Air corroding Glafs 433 

4 . Common Air affeSted by heated ^ick- 
\fiher — ■ — 434 

4. Of the Mixture of the Vitriolic ana 
the Nitrous Acids - - 336 

5. Of a Solution of Copper in firong 
nitrous Acid - - 441 

6. Of Air from Minium, diffolved in 
Spirit of Salt - ... ^^2 

7. 'Experiments with Froji - 443 

8. Of a Saline Subftance formed by Earth 
of Alum andfxed Air - . ' 44 j 

9. Remarks on the Article Gas in the 
new Edition of Mr, Macquer'j Dic-^ 
tionary of Chemijiry - 446 

Sed;. XL. Experiments and Obfervations 
made fince the preceding Friges went to the 
Frefs - - - 450 

• § ^- Q/* ^'*^ ^f Vitriol impregnatea 
with nitrous Vapour - - • - " ibid 

I 2, Of the Colour of the' nitrous Acid /\.^^ 

;. : . . : ■■§, 3, 

The contents. 

§ 3 . Of nitrous Air imbibed by Charcoal 454 

§ 4. Of nitrous Air being, to Appear- 
ancey converted into inflammable Air 455 

§ 5. Of the different Effects of hiver of 
Sulphur, and Flowers of Zinc on coloured 
Spirit of Salt - - - 458 

§ 6. Of the EffeSls of Marine Acid Air 
on Flowers of Zinc, &c, - 459 

The appendix. 

Number I. A Letter from *S/r William 
Lee, Baronet, to Dr. Priestley, on the 
Ufe of Water impregnated with fxed Air, 
in preferving Flefl^ Meat from Putrefac- 
tion - - - 461 

Number II. ExtraSl of a fecond Letter 
from Sir William Lee on the fame Sub- 
jeB, and alfo on the Ufe of fuch Water in 
putrid Fevers - - 462 

Number III. A Letter from Mr. Adam 

W A L K E R , L eSlurer in Natural Philofophy, 

to Dr. Priestley, on the Application of 

fxed Air to an inflamed Breafl - 464 

a 4 Number IV. 

The contents. 

Number IV. A Letter from Mr. 
Becket, Bookfeller in Brtjiol, on the Air 
extraSied from the Water of the Hotwell, and 
on the Air of that City and the Neighbour- 
hood. 466 

Number V. A fecond Letter from Mr. 
Becket to- Dr. Priestley, on the SiibjeB 
of Air from Sea Water. 468 

Number VI. A Letter from Dr. Dob- 
son of Liverpool, to Dr. Percival, of 
Manchefer, on the Air from Sea-water. 469 

Number VII. A Letter from Mr. Ma- 
gellan, F. R. S. to Dr. Priestley, 
071 the Efficacy of fixed .Air for dijfolving the 
Stone, and in putrid Fevers, tried in Holland 


Number VIII. A Letter frojn Dr . Ingen- 
Housz, F. R. S. to Dr. Priestley, on the 
FffeSi of a new Species of inflammable Air, or 
Vapour - - - 474 

Number IX. A Letter from Mr. Bewly 
to Dr. Priestley on the SubjeB of Py- 
rophori » - 479 

T H B 

(MLijjiLi ^iitaaaaQjwwiviifgBifiai 



AVING, in the IntroduSlions to my 
three volumes on the fubjed: of the 

"erent kinds of air, noticed the improve- 
ments I had made in my apparatuSj, with 
the new procelTes I had made ufe of, and 
explained the- figures proper for that pur- 
pofe, I Ihall do the fame in this treatife. 
I have not, indeed, any thing of much 
importance to defcribe j but to perfons who 
have many experim-ents to make, and who 
have little time to give to them, fmall 
improvements are often of no fmall value. 

Fig. I . reprefents the Jh'elf on which I 
place the jars in my trough of water, and 
which is formed on the plan of that of 
the Due de Chaulnes, with a fmall addition. 
It is made to be fixed higher or lower in 



the water, as occafion may require, by- 
means of three bent pieces of copper or 
iron, on which it is fufpended; having 
fmall wedges, or pieces of wood of different 
lizes, for them to reft on. The fhelf is 
about an inch and an half in thicknefs, for 
the convenience of excavating the under- 
iide in the form oi funnels, the orifices of 
which, about a quarter of an inch ir^ 
diameter, appear on the upper fide, as the 
form and fize of the cavity below is exprefiJecl 
hy the dots above. 

The funnels fhould be made as capacious 
as pofiiblej but care fhould more efpecially 
be taken, that no part of them be too flat, 
lefi: any bubbles of air fhould be retained, 
and not pafs into the veiTels placed to 
receive them. 

When frefli air is generated, it is convex 
vient to introduce the tube of the phial in 
which it is produced, quite under the fhelf, 
into the hollow of the funnel. But when 
it happens that the fweep of the tube is top 
fhort for that purpofe, I make ufe of a 
fmall production of the upper part of the 


The introduction. xxvii 
ihelf, with a flit in it, under which the 
ihorter tube may be brought ; and the edge 
of the jar that receives the air, may be 
made to Hide over the place at which the 
bubbles ifTue. 

Fig. 2. is a fide view of a glafs funnel 
fupported by a wooden pillar, rifi ng from 
a bafe, to which a plate of lead is faflened, 
in order to make it fink, and keep its place 
in the water. At the top of the pillar is a 
piece of wood cut in front (but, for that 
reafon, not vifible in this figure) in a con- 
cave form, for fupporting a glafs tube, that, 
refting on the orifice of the funnel, may 
lean againfl it. Both this piece of wood, 
and alfo that which fupports the funnel, are 
made to flide up and down, and are fixed 
by wedges at whatever height is found to 
be mofl convenient. This apparatus faves 
the trouble and inconvenience of keeping 
one's hand in the water for the fake of 
holding the funnel, while the air is pouring 
through it. 

Fig. 3. reprefents an apparatus that would 
jiot deferve a coppejr-plate, but that there 



is often great convenience in little things. 
It exhibits a bafon of quickfilver, fo placed, 
in a frame of wood, as to contain feveral 
glafs tubes, which may be fupported with 
little trouble, and difpofed of without 
materially interfering with each other. In 
this manner I have often more than half a 
dozen in ufe at the fame time. 

Fig. 4. reprefents a cylindrical vejjel m2.d.Q 
of tin, incloling another of iron wire. In 
the outer veffel a charcoal lire may be made, 
furrounding the inner cylinder, which, 
being open at the bottom, will admit the 
upper part of a glafs. jar, fupported in 
whatever manner the operator may find moil 
convenient. Thus ajar, with the air, &c. 
contained in it, may be heated as much as 
the glafs v/ill bear, without giving more 
heat than is neceffary to the lower part of 
it. In this manner alfo, an equal degree of 
heat may be given to every fide of the 
upper part of the glafs. 

Fig. 5. explains the manner in which I 
make an eledrical explofion pafs through 
any fubilance in the form of vapour. It 


The introduction. xxix 
reprefents a glafs fyphon, in each leg of 
which is an iron wire, of fuch a length, 
that there fhall only be about half an inch 
between the heads of them. The fyphon 
muft be filled with mercury, and each of 
the legs inferted in feparate bafons, alfo 
containing mercury. After this, the fub- 
ftance may be introduced into the fyphon 
by means of a glafs tube, and, being lighter, 
it will take its place in the bend of the 
fyphon ; which may then be placed near 
the opening of a fmall furnace, or in the 
apparatus defcribed Fig. 3. when whatever 
lodges in the upper part of the fyphon will 
be converted into vapour, and the explofion 
will be made in it by making the fyphon 
part of an ele(5trical circuit. Mercury itfelf 
may be converted into vapour in the fame 

There is a great variety of methods of 
mixing nitrous and common air, in order 
to afcertain the purity of the latter; among 
which that contrived by Mr. Magellan has 
the recommendation of much ingenuity, 
as well as much limplicity. But the man- 

4 " ner 


ner in which I have been accujfhomed to 
perform that operation is ftill more fimple^ 
though it has nothing to boafi: of with 
refped; to ingenuity. It is neceffary to 
defcribe it, becaufe it is referred to through 
the whole of this work. 

I firfi: provide a phial, containing about 
an ounce of water, which I call t^e air 
meafure. This I fill with air by having 
iirfl filled it with water, and placed it over 
the opening of the funnel in my fhelf ^ and 
when it is filled I Aide it along the fhelf, 
always obferving that there be a little more 
air than I want. The phial being thus 
exactly filled with the air which I am about 
to examine, and care being taken that it be 
not warmed by holding in the hand, &c. 
I empty it into ajar about an inch and an 
half in diameter, and then introduce to it the 
fame meafure of nitrous air, and let them 
continue together about two minutes. I 
chufe to have an overplus of nitrous air, 
that I may be fure to have phlogifton 
enough to faturate all the common air. If 
I find the diminution with thefe meafures 
2 to 

The introduction. xxxi 

to be very confiderable, I introduce another 
meafure of nitrous air j but the pureft de- 
phlogiiticated air will not, I believe, re- 
quire more than two equal meafures of 
nitrous air. 

Sometimes I leave the common and 
nitrous air in the jar all night, or a whole 
day J but always take care that, whatever 
kinds of air I be comparing together, they 
remain the fame fpace of time before I pro- 
ceed to note the degree of diminution. 

When the preceding part of the procefsf 
is over, I transfer the air into a glafs tube, 
about three feet long, and one third of an 
inch wide, carefully graduated according 
to the air-meafure, and divided into tenths 
and hundredth parts j fo that one of the 
latter *\vill be about a fixth or an eighth of 
an inch. Then immerling the tube in a 
trough of water, fo that the water in the 
infide of the tube fhall be on a level with 
the water on the outfide, I obferve the 
fpace occupied by them both, and exprefs 
the refult in meafures and decimal parts of 

a meafure^ 


a meafure, according to the graduation of 
the tube. 

It is fome trouble to graduate a tube in 
this manner j but when it is once done, 
the application of it is extremely eafy. As 
it will feldbm happen that a glafs tube 
is of an equal diameter throughout, I gene- 
rally fill that part of the tube which con- 
tains one meafure, with quickfilver, and 
then weighing it, and dividing it into ten 
parts, put them in feparately, in order to 
mark the primary divifions. This operation 
is performed very readily by having a glafs 
tube drawn out to a fine orifice, in order 
to take up a fmall quantity of quickfilver 
at a time, as it may be wanted. 








OhftrvUfions relating tothel^iTKoxss A c i i>s 
/znd efpecially the Colour of it. 

IN my third volume of Obfervatiojjs 
on Air, I related feveral experiments to 
afcertain the ftrength of the nitrous acid, 
as depending upon the circumflances in 
which it was made, and others relating to 
the colour of it, efpecially when I made 
this acid by impregnating diftilled water 
with the nitrous vapour ; in which cafe it 
iirfl became blue, then green, and laftly 
yellow, I alfo obferved that,, at the be- 

B ginning 

2 Ohfervations on 

ginning of the common procefs for making 
nitrous acid, it was frequently a little 
orange coloured, then a pale yellow, and at 
the laft orange coloured again ^ but that a 
little phlogiflic matter in the materials 
would always make the whole produce of 
a deep orange colour. I have iince that 
made many more ohfervations relating to 
the colour of this acid j and I think I have 
decifively proved, that neither this acid, 
nor the muriatic, have, naturally, any more 
colour than the vitriolic acid, or than water 
itfelf; being able to give them colour, 
change it, or wholly take it away at plea- 
fure; and fome of the circumftances in 
which thefe changes take place are not a 
little remarkable. 

The fads that I fhall relate prove that it 
Is either phlogifion, or mere heat, that gives 
colour to this acid, that this colour may alfo 
be all expelled by heat ; but that continuance 
of heat will give it more colour, and deepen 
it at pleafure, fo that more heat, in glafs 
velTels hermetically fealed, feems to have 
the fame effed: with phlogiilon. But,. 


the Nitrous A^iJ. ^ 

Snore probably, heat afFeds it in fuch a 
manner, as to develope, as it were, the 
phlogifton it contained before, and put it 
into a ?iew Jiate, rendering that part of the 
acid to which it is attached both more vo- 
latile, and alfo difpofed to refle6t the rays of 
light in a particular manner -, whereas, be- 
fore this ad:ion of the heat, the phlogifton 
was latent^ at leaf!:, did not evidence itfclf 
h"^ thofe particular effedls. 

On the firft of AugufI; 1777, I refumed 
my experiments on this fubjed:; when, 
having provided a fand furnace, to be kept 
hot for a confiderable time, for many pur- 
pofes that will be mentioned in the courfe 
of this volume, I put a quantity of flrong 
and pale coloured fpirit of nitre into a glafs 
tube, about an inch in diameter, and three 
feet long ; and, fealing it hermetically, I 
placed it in the warm fand. Taking it out 
after fome time, I found it orange coloured; 
and though it was more deeply coloured 
while it continued hot than it was after- 
wards, it retained fo much of the colour, as 
to ,be ever after of as deep an orange colour 

^. Obfer'Dations on 

as fpirit of nitre is generally found to be.- 
And though before this procefs the vapour 
rifing from it was quite colourlefs, there 
being nothing vilible above the furface of 
the acid^, in the phial from v^hich it w^as 
taken, the v^hole tube (which I have ob- 
ferved was three feet in length) was Uni^ 
formly fill-ed with the dark orange coloured 

This procefs being performed in a glafs 
tube hermetically fealed, I was fully fatis- 
fied, that this colour which the acid had 
affumed could not be owing to any 
thing befides heat. That it was tidx 
owing to any thing peculiar to the glafs of 
lead, of which, in a great meafure, flint 
glafs confifls, was evident from obferving 
the fame effed on the acid when the expe- 
riment was made in common gfefen,- or 
bottle glafs. 

Having about the fame time expofed to a 
"heat of fome continuance feveral quantities 
of blue and green fpirit of nitre, it may not 
"be improper to note the refults of thefe 
experiments in this place. In one 
2 inftance. 

the Nitrous Acid, ^ 

inflance, the green fpirit of nitre became 
orange coloured ; but when it was cold it 
was almoft as green as at firft, though there 
was evidently a mixture of yellow in it. 

When I had expofed a quantity, of blue 
fpirit of nitre in a long glafs tube a few 
days, the blue colour was barely perceiv- 
a})le. It was placed in the fand furnace on 
the 23d of Auguft, and on the 30th of 
September following it was entirely colour- 
lefs, and had no vifible red vapour over it 
when cold. This acid was very weak, 
otherwife, I doubt not, the yellow or orange 
colour would have become apparent. 

I alfo expofed to a very moderate heat a 
fmall phial with a ground ftopper, almoft 
filled with a deep blue nitrous acid, when 
it prefently alTumed a deep green, and when 
it was cold it refumed its former blue 
colour. In this experiment the heat had 
jiot been continued fufficiently long to pro- 
duce a permanent change of colour. For, 
having expofed to a moderate heat, in a 
long glafs tube, hermetically fealed, a 
quantity of blue nitrous acid, it loft its 
blue colour, and afTumed a yellow one; 
B 3 and 

6 Ohfer^ations on. 

and when it was cold the blue colour did 

not return, except in the fmalleft degree. 

I did not, however, come to this con- 
clulion concerning the caufe of the change 
of colour in this acid in the fummary man- 
ner aboye defcribed^ but in confequence 
of a feries of obfervations, attended with a 
variety of circumftances, fome of which 
were remarkable enough. 

A little time before I had made the ex:- 
periments above recited, I had^ begun a new 
mode of examining a variety of fluid fub- 
ftances j which was to put a fmall quantity 
of the fluid into a glafs tube, three or four 
feet long, and fealing it hermetically, to 
expofe the end containing the fluid to as 
great a degree of heat as I found it could 
bear; and to keep it in that heat a confider- 
able time. My defign in providing tubes of 
this length was to give room enough for 
the vapour to expand, and condenfe in the 
remote and cool end of the tube, while it 
was boiling in the other end. 

In this manner I expofed to the influence 
of heat a fmall quantity of fpirit of nitre, 
as Ihad done a variety of other fluid fub- 
"" '^ • fiances, 

the Nitrous Acid. y 

ftances, without any particular expedlation. 

The acid, however, no fooner felt the 
heat than it exhibited appearances that en- 
gaged my attention very ftrongly; and 
whoever v/ill repeat the experiment in the 
fame manner in which I firft made it, will 
find it a very pleaiing one. 

The fpirit of nitre I made uie of was of 
the ilrongeft and paleil fort, Avithout the 
leaft perceivable red vapour over the furface 
pf it. The glafs tube in which it was con- 
fined was about four feet long, and about 
one third of an inch in diameter, and the 
fpa:ce occupied by the acid was two inches 
in length. The tube thas prepared I held 
in my hand, prefenting the end in which 
was the fpirit of nitre to a cortimon fire, 
and holding the tube in an inclined por 
fition. The firfl eifed: of the heat to whicl> 
it was expofed, v^as its alTuming an orange 
colour throughout. After this, a red, or 
deep orange coloured vapour, appeared abov^ 
the furface of the acid, and gradually af- 
cended higher into the tube, at the fame 
time th^t the acid itfelf grew paler, ^nd at 
B 4 length 

2 OhfervatioJii on 

length became quite colourlefs, like water, 
all the colouring matter being, to appear- 
ance, driven out of it. 

This red vapour kept riling higher and 
higher in the tube, leaving a confiderable 
fpace, fome times of ten or tw^elve inches, 
between it and the acid, all which fpace 
was quite tranfparent. This was a very 
pleafing appearance, and it was amufing to 
obferve the fpace occupied by the red va^ 
pour, which extended three or four inches, 
every thing elfe in the tube above and below 
it being tranfparent, and the red fpot itfelf 
receding from the acid as the heat in- 
crcafed, or approaching to it as the heat 

I obferved, however, that by the con-r 
tinned application of heat the quantity of 
red vapour increafed, and the colour grew 
manifeftly deeper 3 when, beginning to ap- 
prehend (though, as I found afterwards, 
without any reafon) that the tube might 
burft, I withdrew it from the fire, and 
prefently faw the red vapour defcend lower 
and lower, till it reached the colourlefs 


the Nitrous Acid* 9 

acid at the bottom of the tube, and, enters, 
ing into it, communicated to it its own orangs 
colour. But when it was quite cold, 
did not, at that time, perceive that the 
acid was of a deeper colour than it had 
been at the commencement of the procefs, 
and no viiible vapour remained upon it. 
To produce a permanent colour, as I ob-i 
ferved before, more time was requifite. 

When one of thefe tubes had been 

thoroughly heated two or three times, and 

the laft time had been expofed to a boiling 

heat for about an hour (the heat having 

been fuch as to keep the acid quite colour- 

Tefs, and likewife to make a large colour- 

lefs fpace above the acid) I let it cool in a 

very good light, and then obferved, that as 

the red vapours defcended, and the con- 

, denfed liquor, highly charged with it, 

trickled down the tube, and mixed with 

the colourlefs acid below, it made waves in 

the acid, fomething like oil in water, or rather 

like the mixture of a flrong acid in water, 

and that this denfer acid defcended in thefe 

vifible waves : to the very bottom of the 

liquor ; 

io Objervations on 

liquor ; and yet when the depth of the acid 
was about two inches, the upper part was 
fenlibly darker coloured by this means than 
the lower. I alfo obferved, that while the 
acid was acquiring its colour, as long as it 
continued tolerably warm, a vapour kept 
ilTuing out of it, and dancing in a beauti- 
ful manner to the height of an inch, or 
two inches, above the furface of it. 

In order to obferve the difference that 
plight be occalioned by expofmg the acid 
to a greater and longer continued heat, I 
kept OAe of thefe tubes fo as to boil vio- 
lently, and be quite colourlefs, for a con- 
liderable time, while I kept another of 
them in fo moderate a degree of heat, as 
only to make the acid of a deep orange 
colour, but never to expel the red vapour 
from it. After fome time tjiat which had 
boiled violently rernained of a deeper orange 
colour than the other, and the tube con- 
tinued to be filled with the red vapour after 
the experiment. In both thefe tubes the 
acid retained a manifeftly orange colour 
when, it was quite cold, and kept it ever 


the Nitrous Acid. n 

after. The tube that had been expofed to 
the greateft degree of heat continued alfo 
quite full of red vapour, and the quantity 
of the liquor was diminiflied about one 
twentieth part, the reft being probably 
combined with the red vapour, or difperfed 
in the tube, fo as not to be colle6ted again. 
I have at the time of this v^riting feveral 
tubes in which this procefs has been per- 
formed, one of which is an inch wide, and 
three feet long ; and though it had only a 
fmall quantity of acid in it, originally of a 
pale colour, and without any vilible va- 
pour, the whole of that large tube is filled 
with the denfeft orange coloured vapour ex- 
pelled in this manner from the pale acid, 
and it has continued fo more than a year, 
without any appearance of the vapour 
^entering into the acid again ; except that 
the colour of the acid, from being of a 
deep orange, which it retained a confider- 
able time, is now become quite green. 
This is alfo the cafe with a pretty large 
quantity of the acid, which had been quite 
pale, but was made of a deep orange, by 


12 Obfervations on 

expofure to heat in glafs velTcls hcrmeti- 
G^ly fealed, and in that ftate transferred 
into a phial with a ground ilopper, and 
which has been kept clofe {hut near a year.. 

I had now tubes filled with the red 
vapour of fpirit of nitre exadly refembling 
thofe of which an account is given in my 
third volume of Obfervations on Air, which 
were made by the rapid folution of bif- 
muth in fpirit of nitre; and I found that 
thefe had the very fame property. For 
whatever part of thefe tubes I heated with 
the flame of a candle, it became of an inr 
tenfely orange, or red colour, while the 
parts both above and below it, which were 
not heated, remained unchanged. 

Having been much pleafed with this ex- 
pulfion of all the colouring matter from g, 
quantity of fpirit of nitre ; and feeing it in 
the form of vapour confined to the fpace of 
four or five inches, in the middle of a very 
long glafs tube, which was quite tranfparent 
above and below it, I made feveral attempts 
to feparate this coloured vapour from the 
fluid, out of which it had been expelled, by 


the Nitrous Acid, lo- 

melting the tube in the intermediate colour- 
lefs fpaee, and fealing it hermetically. But 
thefe attempts were in vain, on account of 
the increafed expanfive force of the vapour 
in that heated ftate. 

I imagined, however, that I might, by 
this means, when the tube was quite filled 
With red vapour, and cold, take it off from 
the acid, and preferve it red and dry, or 
jnearly fo. But in attempting this, I pre- 
fently found that there had been a great in- 
creafe of elaftic matter within the tube. 
For the moment I had a little foftened a 
part of the tube, in order to take it off from 
the reft, the red vapour rufhed out with 
great violence ; the efFedt of the heat on the 
phlogifton in the acid being fuch, as to ren- 
der the vapour to which it was attached 
permanently elaftic, and incapable of being 
any more abforbed by the acid, from which 
it had been expelled. It is poftible, how- 
ever, by this means, to get a tube filled with 
a moderately red vapour. But foon after I 
hit upon a much eafier method of efted:ing 
the fame thing. 


14 Ol;fervations en 

Though I could not feparate the fed 
vapour from the colourlefs acid while it 
was boiling, it was very eafy, I found, by- 
boiling the acid in a iliort tube, or phial, 
to expel all the colouring matter from it, 
and thus to get a quantity of fpirit of nitre 
quite free from all colour j which I accord- 
ingly did, and then imagined that, the 
coloured vapour being wholly expelled from 
it, the acid would always continue colour- 
lefs. And fo, indeed, it did after it was 
quite cold; and it will continue without 
return of colour, and be but little dimi- 
niflied in quantity, or impaired in ftrength, 
fo long as it is kept from the contad: of any 
thing that contains phlogifton, or from 
much heat. But, . to my great furprife, 
at that time, I found that either of thofe 
circumftances would make this colourlefs 
acid refume its former colour, or acquire a 
deeper one than it had before. It was, how- 
ever, by accident, that I firft learned this. 
Having procured a quantity of nitrous 
acid quite colourlefs, I put apart of it into 
a phial which had a common cork (a phial 


thi Nitrons Acid, 15 

with a glafs ilopper happening not to be at 
hand) and not fufpecSting that this circum- 
ftance would afFedt the colour of the acid, 
which was a conliderable diftance from the 
cork. I found, however, after two days, 
when I took out the cork, that the acid 
fmoked \^ery much, an4 had completely re- 
covered its original yellow colour, fo as 
not to be diftinguifhed at fight from what 
it had been before the colouring matter had 
been expelled from it. I then took, a part 
of this acid, and inclofing it in a glafs tube, 
,which I fealed hermetically, expofed it to 
the heat as before, when it became of an 
orange colour ; and refuming the procefs in 
an open tube, 1 drove out the colouring 
vapour once more, and made the acid a 
ifecond time tranlparent. 

I found, however, that a little phlogiftic 
matter has a quicker and more remarkable 
cffedt on this colourlefs acid than mere 
heat. I put a part of the colourlefs acid 
into one of the tubes above mentioned, 
and kept it boiling a whole day before 
"the fire, and the ni^ht following in a fand 


1 6 ObfervatioJis on 

heat> without being able to peixeive any 
fenlible change in it^ though a flight red^ 
nefs was apparent on the firfl: application of 
the heat. But having put another part of 
the fame original quantity of the colbur- 
iefs acid (which fr&m the preceding ex- 
periment will be judged to have been very 
weak) into a phial with a common cork, at 
the diftance of an inch from it, I obferved> 
that in a few hours only, the upper part of 
the atid was become yellow, and the next 
ciioriiing it was yellow throughout, exa(5tly 
like the beft nitrous acid when frefh made. 
But no inilance of a change of colour 
in this acid by heat was fo very remarkable 
as the following. Having'put a fmall quan- 
tity of pale colourlefs acid, into a fhort 
glafs tube, and almoll burying it in the hot 
fand, I found the next morning, that the 
whole tube was quite filled with red vapour, 
and the acid itfelf was quite red, -and per- 
fed:ly opaque, and to appearance a little 
vifcid, like red ink. Neither before, nor 
fince, have I ever feen nitrous acid in that 
ilate. It even retained the fame appearance 


the Nitrous Acid, ij 

which was not orange, but a proper and a 
very deep red. Being quite cold, I could 
examine it at my leifure. It was the only 
appearance I ever had of the kind. 

Replacing the fame tube in the fand heat, 
and taking it out fome time after, the 
acid was of a deep orange while hot, but 
not very deep, and rather of a pale colour 
when cold ; but there was a little whitifh 
matter formed on different parts of the glafs, 
of which a farther account will be givtxi 

I foon found that the clofe confinement of 
the vapour contributed greatly to this change 
in the acid. A quantity of colourlefs acid be- 
ing put into a fhort thick tube hermetically 
fealed, and placed in the fand heat, in about 
an hour had red fumes, and in an hour more 
the acid was orange coloured. Whereas a 
quantity of the fame acid confined in a 
long tube the fame time, and in the fame de- 
gree of heat, had acquired red fumes only, 
while the acid itfelf remained colourlefs. 

In all the circumftances in which much 

heat is given to fpirit of nitre, it neceffarily 

C acquires 

1 8 Obfervafions on 

acquires a deeper colour. This is the reafon 
why, in all my attempts to procure a very 
ftrong fpirit of nitre, by ufing concentrated 
vitriolic acid, and boiling the nitre, in or- 
der to expel the water it contained, it was 
always of an orange colour. For, in this 
cafe, the mixture of the oil of vitriol and 
nitre was attended with great heat. 

I believe that any degree of heat, fuf- 
ficient to throw the acid into the form of 
vapour, will always give it more colour 
than it had before. This I found to be the 
cafe when I rediftilled a quantity of fpirit of 
nitre from frefli nitre, in order to purify it 
from any vitriolic acid that might remain in 
it. The refult of this procefs was an acid 
of a deeper colour, and that fmoked more 
than it did before. It is poffible, how- 
ever, that a fmall quantity of fome matter 
containing phlogifton might have been con- 
cealed in the nitre I made ufe of, though I 
had no particular reafon to fufped: it. 

Having procured nitrous acid in the fe- 
veral ftates above-mentioned, viz, the origi- 
nal pale coloured acid, that out of which 


the Nitrous Acid. ig 

the colour had been expelled by heat, that 
which had been diftilled again from frefh 
nitre, and that which had been pjilogifti- 
cated by heat in clofe veiTels, I tried the 
flrength of them all by the folution of cop- 
per, meafuring the quantity of nitrous air 
that equal bulks of them (all other circum- 
stances being the fame) produced, and ob- 
ferved that a quantity of each occupying 
the fpace of 2 dwts 18 grains of water 
yielded as follows, viz. 

,_,, . . 1 , , , ^ Ounce Meafures, 

The origmal pale coloured 7 

acid, - J ^4- 

The colourlefs, - 1 1 

That rediftilled from nitre, i r 

Tliat coloured by heat, 1 1 

• This highly phlogifticated acid hilled 
very much when mixed with water. The 
produce of air was. more or lefs accelerated 
during the courfe of the folution in all of 
them, but moil of all v/hen I ufed the pale 
coloured acid. I muft obferve that, in 
making this colourlefs acid, I ufed more 
heat than was necelTary, and therefore 
weakened it too much, though it is certainly 
C 2 impoffible 

20 Oifjervattons on 

impoffible to expel the colouring phlo- 
gifton without expelling, at the fame time, 
the acid. to which it is attached. It is fome 
thing remarkable, that the phlogifton, in 
this particular Jlate, fhould attach itfelf 
wholly to one part of the acid only, though 
mixed with the reft of the acid, com- 
bined alfo with phloglfton, but in a diffe- 
rent ftate. Thefe experiments, however, 
fufficiently demonftrate this to be the 

Heat is not necelTary to make fpirit of 
nitre colourlefs. For expofure to the open 
air does the fame thing, and probably with 
lefs difiipation of the acid. During this ex- 
pofure "to the open air, the nitrous acid, if it 
be ftrong, increafes conliderably in bulk and 
weight, in which it refembles the vitriolic 
acid, though this is not in the fmalleft de- 
gree volatile. In order to obferve more 
dillindtly the whole of this procefs, fome 
time in the month of July 1777, I expofed 
to the open air, in a common glafs tumbler, 
about three ounces of orangexoloured fmok- 
ing fpirit of nitre. In a day or two it was 


the Nitrous Acid, 21 

quite colourlefs, but a fly, or any fmall 
fubftance containing phlogifton, falling into 
it, would colour the furface of it again for 
a confiderable time, though at length thefe 
accidents had lefs eifedt upon it. This acid 
kept increafing in bulk to the April follow- 
ing, when the quantity was confiderably 
more than doubled; but from that time it 
began to decreafe, and continued fo to do till 
more than half that it had gained was gone, 
after which it continued very much the 
farpe for feveral nionths. 

The circumftances relating to the white 
matter i which I have obferved was formed 
by the nitrous acid in glafs tubes hermeti- 
cally fealed, and expofed to a continued 
heat, I am not able to explain. I firil ob- 
ferved it in that fhort tube in which the 
phenomena of the col6ur of the acid were fo 
very remarkable, and indeed fingular; but 
afterwards it never failed to make its appear- 
ance whenever the acid had been long con- 
fined, and expofed to much heat, but the 
quantity procured was too inconfiderablq 
to make many experiments upon it. 

C 3 It 

22 Obfervations on 

It was on the 25th of September that I 
obferved this white, or yellowilh, matter in 
the tube above-mentioned. On the 30th of 
the fame month, I obferved that the colour 
of the acid was rather lighter, and beiide 
that whitiih matter at the bottom of the 
tube, there was a fimilar concretion ad- 
hering to the fides of the glafs, juft above 
the furface of the acid, the colour of which 
was partly yellow, and partly green. 

Having got more of this white matter in 
other tubes, I obferved that it was ealily 
fcraped off from the glafs, -.nd left it tranf- 
parent, fo that it feems to be fomething de- 
pofited from the acid, and not an abralion 
of the glafs. It was not at all affed:ed by 
diftilled water, but fpirit of fait diffolved it 
entirely, and became of a yellow colour 
inclining to orange. Applying the flame of 
a candle to that part of the glafs tube on 
which fome of this white matter lay, it was. 
diffolved, and difperfed in white, not red 
vapours. An earthy pellicle remained, not 
ealily affedied by heat, but it was difperfed 
when it was made red hot with a blow pipe. 


the Nitrous Acid, 23 

This pellicle adhered firmly to the glafs, but 
m time it was completely diflblved by fpirit 
of fait, which aifumed the colour above- 

It is pretty evident, from this obferva- 
tion, that this matter did not really con- 
tain fpirit of nitre as fuch. For had it 
contained the proper nitrous acid combined 
with any earthy matter, as the calx of the 
lead in the glafs, the fpirit of fait could not, 
I apprehend, have decompofed it. In other 
refpeds it had very much the appearance of 
minium become white by imbibing nitrous 
vapour. But this is not at all afFed:ed by 
fpirit of fait. 

It was evident, however, that wherever 
this white matter was formed, the quantity 
of the acid was diminiihed, fo that it looks 
as if the acid itfelf was deftroyed, and con- 
verted into fomething of a different nature. 

On the 6th of January 1778, I obferved 
that a long glafs tube, one fourth of an inch 
in diameter, into which I had put as much 
fpirit of nitre as filled about half an inch of it^ 
gild wliich had been expofed to the fand heat 
C 4 about 

24 Ohfervations on 

about two months, had no moiflure in it, 
except a very little that adhered to the fides, 
too fmall to run down the tube. The tube 
continued full of red vapour, and fo it 
continued feveral months, but not fo deeply 
coloured as it had been fome time before, 
and about half an inch at the bottom o£ 
the tube had a flight incruftation of the 
white matter mentioned above. Th&t the 
volatile matter was diminiihed, was evident 
from my obferving that when I melted a 
part of the tube with a blow pipe, the glafs 
was prefled ftrongly inwards, whereas 'be- 
fore the formation of this white matter, 
when I foftened any part of the tube in 
this manner, the expanded vapour would 
burft it open, and rufli out with great 

After eight or ten months, I obferved 
this tube to have lofl the greateft part of 
its colour, and in a few weeks more it was 
quite colourlefs. Examining it more nar- 
rowly, I obferved an exceedingly minute 
crack, about half an inch above the bottom 
of the tube. However, w^hen I foftened 

* the 

the Nitrous Acid. 25 

die glafs with a blow pipe it was ftrongly 
prefled inwards, fo that there feemed to 
have been little or no communication be- 
tween the air within and that without. 
When that crack was made I cannot tell ; 
and I muft leave it to the opinion of my 
reader, whether it be probable, all cir- 
cumftances coniidered, that the acid had, 
in any meafure, efcaped by that crack. 

I have obferved, in my former publica- 
tions, that common air is phlogifticated 
by continuing a confiderable time involved 
in the red vapour of fpirit of nitre. This, 
contrary to my expedtation, I alfo found to 
be the cafe with the colourlefs, or invifible 
vapour of fpirit of nitre, after all the colour- 
ing phlogiflic matter had been driven out 
of it. Air that had continued only two 
days in a phial with a glafs ftopper, which 
contained fome of this colourlefs acid, was 
fenfibly lefs affe<fled by nitrous air than 
common air was ; and the air that had been 
confined in the fame glafs tube in which 
fome of the colourlefs nitrous acid had been 
placed in the fand furnace only two days, 


2.6 OhfErvations on 

though the heat had been fo fmall as to have 
produced no change of colour in the acid, 
was fo much phlogifticated, that one mea- 
fure of it, and one of nitrous air occupied 
thefpaceof 1.81 meafures. 


Of the Nitrous Acid Vapour. 

IN the third volume of Obfervations on 
Air, I obferved the remarkable eifedls 
of impregnating oil of vitriol w^ith nitrous 
acid vapour. It was one of the laft obfer- 
vations that I made before the printing of 
that volume. 

Having impregnated a larger quantity of 
the oil of vitriol than I made ufe of in 
thofe experiments, I left fome of it in a 
large phial, w^ith a ground flopper, among 
other phials containing things for which I 
had no immediate ufe. But though my 
procefs was over, that of nature was not. 
Happening to be looking at it on the 19 th 
of March following, perhaps about fix 


the Nitrous Acid Vapour, 27 

months after the impregnation, I found what 
I was far from having expedted, 'uiz. that 
almofl the whole was c'ryftallized, a very 
fmall part only of the contents of the phial 
remaining liquid, The cryftals looked ex* 
a(5tly like ice, and exhibited all the appear- 
ances that I had before obferved to attend 
the fimple im.pregnation of the vitriolic 
acid with nitrous vapour, but in a much 
more elegant manner. For on dropping a 
piece of this ice into pure water, it be- 
came green, and effervefced with great vio- 
lence ', and, what made a beautiful and 
flriking phenomenon, all the water in 
which the ice was diifolved began inflantly 
to fparkle, with the. fpontaneous and co- 
pious produdion of air. With the help of 
a little heat, this produ(Stion of air was ^o 
great, that the quantity was more than a 
hundred times the bulk of the ice that had 
been diffolved. It was the pureft nitrous 
air. In fa6l, a great quantity of nitrous 
vapour was, as it were, imprifoned in this 
oil of vitriol, and being fuddenly fet loofe, 
on being plunged in the water, it impreg- 

28 Obfervations on 

nated the water in the fame manner as I 
liave obferved that the nitrous vapour never 
fails to do. 

The application of heat made this ice 
emit a denfe red fume -, but holding a quanr 
titf of it in a glafs vefTel over a candle, it 
prefently melted, emitting bubbles j and 
then, letting it ftand to cool gradually, it 
cryftallized very fuddenly, when it was 
about blood warm. It was in this fecond 
congelation much more opaque, and denfer 
than it had been in the fqrmer. When 
this ice was dilTolving with heat, the fume 
it emitted was not red, but white, and 
exceedingly denfe, like oil of vitriol in va- 
pour. After it had been kept diflblved, 
and in a boiling heat, fome time, it did not 
cryflallize afterwards, but continued fluid 
and tranfparent; being then, probably, 
mere oil of vitriol. 

I h^ve not yet been able to inveftigate all 
the circumftances neceffary to this remark- 
able cryftallization, having originally found 
it when I had no expectation of any. fuch 
thing, and haying often failed to find it when 

I have^ 

the Nitrous Acid Vapour, 2.g 

I have expe(5led it the moft. All that I can 
do, therefore, is to recite what I have ob- 
ferved, with all the circumflances that I 
can recoiled: relating to the appearances. 

I had kept about half an ounce meafure of 
oil of vitriol, not quite faturated with ni- 
trous vapour, in a fmall phial, with a ground 
i^opper, about a year, in all which time it 
had ihewed no tendency to cryftallization, 
and from its imperfed: impregnation I had 
fliot fixpeded it. I was intending to com- 
plete the impregnation, and, looking at the 
phial, had taken out the ilopper, and put 
it in again, deferring the procefs till the 
day following, when I found the phial al- 
mofl filled with the moil beautiful cryftal- 
lizations imaginable. 

Their form, as nearly as I can cjefcribe 
it, was that of a feather. They were about 
twenty in number, fome of them as large as 
the phial could contain, and many of them 
parallel to each other, but others lying in 
.different diredions. The two parts, as it 
were, of the feather made an angle with 
each other of about 160 degrees, and ^aclj 


§0 Obfervations on 

of the iingle fibres that compofed the fea- 
ther, but which v/ere conne<5ted, like the 
toes of a duck's foot, by the fame fubflance 
(but thinner, and more tranfparent than the 
reft) made an angle with the ftem from, 
which they arofe of about 45 degrees. A 
more beautiful appearance can hardly be 
imagined, and I am afraid I fhall never fee 
the like again. 

Having obferved thefe cryftals fome days, 
and feeing no farther change in them, or in 
the liquor which covered them, and which 
rofe about a quarter of an inch above them, 
I poured the liquor from the cryftals, and 
for fome time they continued upright, ex- 
haling a red vapour, which filled the phial, 
and at length very much clouded and ob- 
fcured it. This liquor exadlly refembled 
ftrong fmoking fpirit of nitre, and feemed 
to have nothing of the vitriolic acid in 

After fome time the cryftals feemed to de- 
cay, and funk down in the phial, filling up 
all the interflic^s that had been among them, 
fo as to make one compadl mafs, without 


the Nitrous Acid Vapour, 31 

any thing of the beautiful appearance that 
they made before. Hoping to repair the 
injury they had fuilained, and to reilore 
their beauty, I filled up the phial with 
frefh oil of vitriol ftrongly impregnated 
with nitrous vapour, but it had no fenfible 
effed:, nor did any more cryilals of the fame, 
or of any oth^r form fhoot out from them 
in many months. 

Having another phial of oil of vitriol 
partly impregnated with nitrous vapour, and 
of about the fame ftanding with the former, I 
examined it, and found it half filled with 
cryftals, but thefe lay all confufedly at the, 
bottom of the phial, and though in fepa- 
rate pieces, of no uniform fhape. 

After this I impregnated three different 
quantities of oil of vitriol with nitrous va- 
pour. One was very ftrongly concentra- 
ted, having diflilled off about half the quan- 
tity of the befl common fort, the fecond 
was both diftilled and concentrated, and 
the third was only of a medium ftrength, 
and the common fort, but colourlefs. I kept 
all thefe in the fame fituation, and in about 
5 a fort- 

^^ Olffervationi bh 

a fortnight that which had been limply 
concentrated began to cryftallize, and in 
about a fortnight more the phial was half 
filled with cryflals> fome of them in the 
form of feathers, but lying in different 
directions, and not detached from each 
other ; but forming a compad: mafs. 

In this ilate I left them, being obliged 
to be abfent from my laboratory about 
three months ; and at my return I found 
all the phials full of cryjfbals, but generally 
in folid malTes, with few fuch feathers as 
I have defcribed above, and thefe veryfhort 

Imagining that this lingular cryllalliza- 
tion might poflibly be accelerated by ex- 
pofing the impregnated vitriolic acid to 
heat, I took a quantity of it which had 
continued a confiderable time without 
cryllallizing, and confined it in a glafs 
tube three feet long, and half an inch ia 
diameter. Then holding it to the fire, I 
obferved that the acid emitted red vapour, 
which filled the whole tube, exactly as 
would have been the cafe with fpirit of 


the Nitrous Acid, 3 j 

iVtre itfelf. When it was cold many fmaU 
cryftals were fcattered all over the tube 
above the furface of the liquor, and the 
upper part of it was red ; being, I fuppofe, 
the fpirit of nitre that had been driven out 
of it by the heat, as being more volatile 
than the vitriolic acid. 

I have already obferved that, to ap- 
pearance, the vitriolic acid impregnated with 
nitrous vapour was nothing but nitrous 
acid, after the complete formation of the 
cryAals, and by experiment I found it to 
be nothing elfe. For diluting it with 
water, and diiTolving iron in it, in a phial 
with a ground ftopper and tube, in the 
manner in which I ufually produce nitrous 
air, it yielded this kind of air only, without 
any mixture of inflammable air -, which I 
have formerly obferved is the cafe when 
the vitriolic and nitrous acids are mixed to- 
gether, and employed in the folution of 
iron, the nitrous air coming firft, and the 
inflammable air afterwards. 

Here, indeed, a very fmall quantity of 

the lafl produce burned with a lambent 

D flame 3 

34 Ohfervatmm on 

flame ; but this I have obfefved to be th®' 
cafe with the laft produce from iron and the 
nitrous acid only, when the procefs tvas 
urged, as it was now, with the flame of a 
candle. The water, when this acid was 
mixed with it, fparkled very much, 
yielding, I doubt not, nitrous ai'r. But this 
circumftance only proves it to have been 
highly charged with phlogifticated nitrous 

Here then is a cafe in which the nitrous 
acid appears to have a ftronger affinity with 
water than the vitriolic : for in a courfe of 
time, it intirely expells the vitriolic acid 
from it, and unites with it itfelf ^ all the 
vitriolic acid being precipitated in the 
cryftals that confift of both the acids. 

At the time of my laft publication, I 
filled tubes and phials with the red nitrous 
vapour, by means of the rapid folution of 
bifmuth in fpirit of nitre, which is a 
troubleforhe operation, when the tube is to 
be fealed hermetically after being filled 
with the vapour. The manner in which I 
fucceeded in this experiment would be te=- 


the Nitrous Acid. ^^ 

Atom to defcrrbe, and it would be unne- 

cefTary, as I have fince efFedted the fame 

thing in a much eafier manner* For red 

lead converted into a white fubftance (as 

I have obferved 'it to be by impregnation 

with the nitrous vapbiir, and which may 

be kept in that ftate without deliquefcing 

any length of time, and without feeming 

to be difpofed to part with any of the 

Vapour which it has imbibed in the 

temperature of the atmofphere) readily 

emits it in a melting heat. I therefore put 

^ fmall- quantity of this white minium 

into a glafs- f ube clofed at one end; then, 

holding it to the fire, make it emit the 

red vapour, till the whole tube is filled 

with it ; and having the other end of the 

tube drawn out ready for clofing, as foon 

as the vapour begins to iflue out of that 

end, I apply my blow pipe and feal it. 

By this means I conclude that the tube 
is filled with a pure red vapour, without 
that mixture of nitrous air, and perhaps 
common air alfo, which I could not ex- 
clude before; and when this is done, I 
D 2 can 

36 Obferijatlons-07i 

can eafily, afterwards, melt off that part of 
the tube which contains the minium, fo 
that it does not at all appear in what manner 
the tube was filled with the vapour. A 
tube thus prepared will become of a deeper 
colour with heat, and paler with cold, 
exa-d:ly as the tubes filled in the manner 
defcribed in my third volume. A little 
moiflure is expelled from the white 
minium along with the red vapour, hut it 
is very inconfiderable. 

This white minium never fails to be 
produced when, in anycircumftances, the 
common minium is fufficiently impreg- 
nated with nitrous vapour. In making a 
quantity of dephlogifticated air from the 
com.mon minium and fpirit of nitre, I 
once filled a whole gun barrel with the 
materials ; and when I emptied it, after 
the procefs, in which the bottom of the 
gun barrel only had been afFedled with the 
heat, I found part of the minium, at a, 
fmall diftance from the place that had been 
the hotteft, perfed:ly white, while that 
from which the air had been expelled was 


the Nitrous Acid. ^y 

yellow, as ufual, and that whicli was far- 
ther from the heat than the white minium 
was almofl black. 

Having had a flight fufpicion that the 
whitenefs of this minium might poilibiy 
have been occafioned by fcmething from 
the hifmuthy carried over along with the 
nitrous vapour produced in the folution cf 
it, I made a Similar procefs with the folu- 
tion of iron, and /found that it had the 
very fame effedt as the folution of bifmuth, 
converting the minium into a white fub- 
ftance, exadly like that which I had pro- 
cured before. It is, therefore, the pure 
cfFed: of impregnation with nitrous 
vapour, but certainly a very extraordinary 
one, and it may be well worth while to 
extend the procefs to various other folid 

Since my laft publication I have im- 
pregnated feveral other liquid fubflances 
with nitrous vapour, and the refults in 
fome of the cafes are not a little remark- 
able, efpecially with refpe(5t to die colour 
communicated by this means. 

D 3 The 

3^ Obfervattons on. 

The phofphoric acid is prefently faturat-< 
ed with nitrous vapour, and aflumes a deep 
indigo blue colour. 

Radical vinegar is alfo foon fatu rated 
with this vapour, and aiTumes a light blue. 

Spirit of fait faturated with frefli 
minium, fo as to be of a yellow colour, 
becomes of a deep orange when impreg"^ 
nated with nitrous vapour. 

Spirij: of fait faturated with white 
minium, made {o in confequence of the 
colour being extracted from it by the fpiri| 
of falt^ aiTumes a light blue colour by being 
impregnated with this vapour. 

Spirit of fait faturated with red precipi- 
tate, or the precipitate per fe, aiTumes a 
green colour. 

Spirit of fait faturated with ilowers of 
zinc acquires a blue colour, deeper than a 
Iky blue, but not fo dark as the blue of 
the phofphoric acid„ 

iD Hi v-- X. ^ 

th Nitrous Acid, 39 


Some Phenomena attending the Solution of 
Metals in Nitrous Acid, 

AS the difcovery of fixed air in cal- 
carious fubftances threw new light 
upon many phenomena 'm chemiflry, in 
like manner the difcovery of every other 
jkind of air, and indeed of every property 
of any of them, muft throw light upon 
^hofe procefTes in which they are con- 
cerned. Not being a profcfTed chemift, 
and attending only to fuch articles in that 
branch of knowledge as my own purfuits 
^re particularly conned;ed with (though 
thefe neceflarily grow- more various and 
extenfive continually) fuch illuilrations of 
chemical procefTes are not fo likely to occur 
to me, as they are to others, who by their 
profeffion give a general attention to every 
thing within the whole compafs of che- 
miftry. Such, however, as I have had oc- 
cafion to attend to, and which I imagine I 
D 4 can 

40 Ohfervutions on 

can throw any light upon, I ihall not fail 
to mention. 

There are feveral fads relating to the fo- 
lution of nietals in fpirit of nitre, which 
could not have been underllood without the 
knowledge of nitrous air -, and yet, though 
feveral of them are very remarkable^ I do 
not find that even the phenomena them- 
felves, and much lefs the difficulties at- 
tending the folution of them, have been 
fo much as noticed. I am perfuaded, 
however, that an attention to the nature of 
this remarkable kind of air will contribute 
greatly to the inveftigation of the conftitu- 
tion of the feveral m.etals, and the explana- 
tion of m.any phenomena attending their, 
decompofition, and confequently their com- 

Having had frequent occaiion to dilTolve 
mercury in fcrong fpirit of nitre, in order 
.to procure from it nitrous and dephlogifli- 
cated air, and to note the quantity of the 
metal revivified afterwards, I could not help 
being very particularly ftruck with fome 


the "Nitrous Add. 4t 

phenomena in the folution, which are as 

The moment that ftrong fpirit of nitre 
is poured upon quicklilver, the folution is 
inftantly very rapid. But though it is 
known that one method of procuring 
nitrous air is by the folution of this metal 
in the nitrous acid, not a fingle bubble of 
any kind of air is feen to be formed ^ at 
leaft none rifes through the acid. Pre- 
fently, however, one may perceive, that 
very large bubbles of air are formed, but 
they inftantly difappear, and nothing re- 
mains of them but the fmalleft fpecks ima- 
ginable, to rife to the top of the acid. 
^y degrees, the acid near the mercury be- 
comes of a deep orange colour, and then 
through this part of the acid the bubbles 
pf air afcend freely -, but the moment they 
come to the fuperincumbent pale coloured 
acid, they collapfe into thofe fmall and 
barely perceivable points, yielding no air 
that can be coileded in any fenfible quan- 
tity. And it is not till the whole quantity 
of the acid is changed from a pale to an 

c orange 

4t. Obferi^atlons on 

oraage colour, that any nitrous air can be 
colleded. Then, however, the bubbles 
rife freely to the top of the acid, and, 
mixing with the incumbent common ai^ 
exhibit an orange colour by their de* 
compofition on mixing with it. Then, 
alfo, a flrong fmell of fpirit of nitre is 
perceived, as it always happens when ni^ 
trous air is let loofe to mix with the air of 
the room in which we are breathing. 
Whereas, immediately before, no fmell 
was perceived, and the common air in- 
Cumbent on the mixture was quite colour- 

Had thefe lingular phenomena been no^ 
ficed by any chemift before the difcovery 
ef nitrous air, I cannot imagine what hy- 
pothelis he would have formed for the ex- 
planation of them. Whatever it had been, 
it mull have been very wide of the truth , 
whereas the whole proeefs admits of the 
eafiell explanation imaginable by the help 
of my obfervations on the decompofi- 
tion of nitrous air by the nitrous acidy 

Vol, ill. p. 121, - . 


tke Nitrous Acid^ ^5 

Nitrous air is actually formed the mo- 
ment that the folution begins, but it is 
inftantly decompofed by the ftrong fpirit 
of nitre in contadt with it. By the ad- 
dition of the phlogiflon contained in the 
nitrous air, the pale fpirit of nitre aiTumes 
an orange colour, and it is then much lefs 
able to decompofe the nitrous air j which, 
therefore, rifes in bubbles through it, and 
is not decompofed till it comes to the 
region of the pale acid lying upon it. But 
when the whole body of the acid is faturated 
with phlogifton, then, and not before, the 
bubbles of nitrous air pafs freely through 
it, and may be collected. 

On this account, it is not eafy to afcer- 
tain the exadt quantity of nitrous air yielded 
by the folution of mercury, and, for the 
fame reafon, of other metals too, in ftrong 
fpirit of nitre ; becaufe allowance muft be 
made for the quantity that will be imbibed 
by the acid itfelf, which muft be faturate^ 
before any can be colledied : whereas, when 
the acid is much diluted with water, it is, 
not fo capable of decompoling this air, and, 


ij.4 Obferudfions on 

therefore, in general, it may be colled:ecl 
from the moment that the folution begins. 

It is very remarkable, that when copper 
is dilTolved in pale fpirit of nitre, eveii di- 
luted with much water, though the folu-; 
tion is evidently the moft rapid at the firft, 
the produce of air is very trifling for a con- 
fjderable time, and the quantity colleded 
increafes very gradually ; whereas when the 
orange coloured acid is employed, in the 
fame diluted ftate, the nitrous air is col- 
leded immediately, and the produdion is 
the mofl copious at the firft. 

When I difTolved a quantity of copper in 
flrong fpirit of nitre half diluted with water, 
no air wh'ktever was produced, though the 
metal was completely diifolvedj, 

When, in the folution of mercury, I 
ufed the green fpirit of nitre, inftead of 
the pale coloured and ftrongeft acid, the 
phenomena were not materially different 
from thofe defcribed above. The lower 
part of the acid next to the mercury af- 
fumed a deeper green, but it never became 
orange coloured. 

S E C« 

Nitrous Air* 4| 


Of the Changes to lohich Nitrous Air is 

BOTH nitrous and inflammable air con- 
tain phlogillon, and, as will be feen 
in its proper place, they probably contain 
nearly equal quantities in equal bulks -, but 
as their properties are remarkably different, 
their conilitution muft be different alfo -, 
the phlogifton which enters into the com- 
polition of them both being combined in 
them in a very different manner. In fbme 
cafes nitrous air parts with its phlogiflon 
more" readily than in:flammable air, but in 
other refpe(3:s inflammable air is the more 
eaiiiy decompofed of the two. The phlo- 
giflon of nitrous air immediately quits it 
on the contacft of common air, when it is 
even quite coldj whereas the phlogiflon of 
inflammable air will not leave it to join 
the common air except when it is very 
hot 3 but it will be feen that inflammable 
air parts with its phlogiflon to the glafs of 

^5 Obfervations btt 

lead in the compofition of flint glafs in ci^-* 
cumilances in which nitrous air undergoes 
no change whatever. I kept a quantity of 
nitrous air in a tube of flint glafs, herme- 
cally fealed, buried in hot fand, but not 
fuffi-cient to melt the glafs, twenty days 
without any fenlible change in the bulk or 
quality of the air. In the upper part of 
one tube filled in this manner there wa^ 
fbmething like fmall cryflallizations, but 
they might poflibly come from a fmall 
quantity of the quickfilver accidently lefi 
iixi the tube. But whether nitrous siir wilf 
he decompofed by quickfilver in this ftate 
af heat and confinement I did not try. In^ 
deed. I did not examine whether what I faW 
were properly cryflallizations, or not. 

I kept both, nitrous air and inflammable 
air very hot in contad: with quickfilver 
widi liberty to expand, and did not find- 
that either of them underwent any change. 
Ai quantity of. nitrous air I expofed feveral 
hours for: thrive days to a degree of heat 
which kept: the quickfilver in a ftate of va^^ 
pour, the firfl: and fecond day to the fame' 


Nitrous Air, 

quickfilver, and the third day to frefh quick*^ 
iilver j but the dimenfions of the air, and 
its property of affedting common air, con- 
tinued the fame. The procefs is defcribed 
in the Introdudion. 

The addition of fleam of water to the 
nitrous air in this ftate of heat and expan- 
fion made no difference in the refult of the 
experiment, though they continued toge-' 
fher upon quickiilver more than two hours. 
The fmall alteration that I found in the 
nitrous air might be afcribed to its having 
been transferred from the trough of water 
to the bafon of quickfilver in a bladder. 
I varied the experiment by confining the 
nitrous air in a glafs jar inverted in a pan 
of water, which I made to boil, in order 
that the hot fteam might pervade the whole 
mafs of the air, which it eifedlually did, 
as it appeared by its having expelled a very 
great part of it. After the procefs, which 
continued about an hour, the nitrous air 
had loft nothing of its power of diminifh- 
ing common air. On the contrary, it 
2 feemed. 

48- Obfervations 6n 

feemed, to be rather improved than to 

have had its virtue impaired. 

Since my lafl publication I have obferved 
feveral more circumftances relating to the 
decompolition of nitrous air, fome of w^hich 
are remarkable enough. 

In the preface to my third volume I men- 
tioned in general, the quick abforption of 
this air by a folution of green vitriol, 
which I had juft then obferved. I ihall 
here mention the particulars of that obfer- 

Having dilTolved a quantity of green 
vitriol, and put it into a phial, with its 
mouth inverted in a bafon of the fame, 
and having admitted a quantity of nitrous 
air to it, I began to agitate the folution, in 
the fame manner as in the procefs for im- 
pregnating water with fixed air^' when I 
obferved that the nitrous air, in thefe cir- 
cumflanceSj was abforbed much more 
readily than fixed air is by water. I even 
made a quantity of this folution abforb 
more than ten times its bulk of nitrous 
air, v/ithout any very fenfible approach to 


Nitrous Air. 49 

tion. The folution became black by this 
procefs ; but when a fmall part of it was 
viewed by the light of a candle, placed be- 
yond it, it looked red. The tafte of the folu- 
tion was acid, ov/ing, no doubt, to the mix- 
ture of nitrous acid, which it had acquired, 
in confequence of the decompofition of the 
nitrous air. 

When this impregnated folution was ex- 
pofed to the open air, large green cryilals 
were formed at the bottom of the vefTel, 
an.d all the black colour intirely difappear- 
ed. But when thefe cryftals were formed at 
the bottom of a very tall velTel, they were 
much blacker, and did not even become 
green on being expofed afterwards to the 
open air, any more than thofe which I ex- 
pofed to nitrous air itfelf ofi quickiilver. 

The changes of colour, and all the phe- 
nomena of the cryftals, were evidently 
owing to thefpirit of nitre contained in the 
nitrous air, and fet at liberty in its decom- 
pofition. For a few drops of the acid itfelf 
produced the fame eife^s, in all refpe(5ts, on 
this folution. 

E / Conceiving 

50 Obfervattons on 

Conceiving that the principal of thefe 
phenomena mufl have arifen from the 
affinity between nitrous acid and iron, I 
agitated nitrous air in a natural chalybeate 
water, when it prefently became of a 
brownifh colour, which feemed to be a con- 
firmation of my fuppoiition. 

I alfo made another experiment in which 
the nitrous acid might fhow its affinity to 
iron in a manner fomewhat limilar to this. 
I firil: faturated a quantity of water with 
fixed air, then with iron, and afterwards 
impregnated it with nitrous air. The re- 
fult of this experiment was, that the folu- 
tion afTumed a colour between green and 
yellow i but it did not abforb much more 
nitrous air than water unimpregnated with 
fixed air, or with iron, would. have done. 

The nitrous air which I had hitherto 
made ufe of in thefe experiments was made 
from copper, but when I ufed that which 
was made from iron, which is an ingre- 
dient in green vitriol, the efPedt was not at 
all different. The folution of the vitriol ab- 
forbed nitrous air with the fame rapidity as 


Nitrous Air. ^i 

It did that which was made from copper, 
and the fubfequent phenomena were alfo^ 
in all refpeds, the fame. 

I then agitated nitrous air in folutions of 
blue and white vitriol, the former of which 
is known to be compofed of copper, and 
the latter of zinc. The refult was, that 
the colour of both thefe folutions became 
'prefently very dark, the former changing 
into a deep green, and the latter into a kind 
of brown. Not more than between one 
half and one third of the air (which was 
about one fourth of the contents of the 
phial I made ufe of) was abforbed in either 
of thefe cafes, which is very far fhort of the 
effect of the folution of green vitriol on the 
fame kind of air. 

. It made no difference whether the nitrous 
air was procured from iron or from copper, 
in any of thefe experiments. For the folu- 
tion of green vitriol, as I have obferved, 
decompofed nitrous air made from iron 
juft as readily as that which was made from 
copper j and, on the other hand, the folu- 
E 2 tions 

^2 Obfervations on 

tions of blue and white vitriol were af- 
fcdled in the very fame manner by nitrous 
air made from copper, as by that from iron. 

The folution of white vitriol depolited a 
white and flocculent matter, and then was 
tranfparent like water ; but, being impreg- 
nated with nitrous air, it prefently became 
of as dark a colour as when it had been im- 
pregnated before that depoiit was made. 

Spirit of nitre dropped into the folution 
of blue or white vitriol made little or no 
change in their colour. 

All the folutions of vitriol which had 
their colour changed by the impregnation 
with nitrous air recovered it again by 
expofure to the common air. This was evi- 
dently efFe6ted by the efcape of that phlo- 
giflon, which had contributed to the deep- 
nefs of their colour. To afcertain this, I 
filled a phial about three fourths full of the 
folution of green vitriol, made blaci? by the 
decompolition of nitrous air, and after about, 
a week, examining the air which had been 
confined with it, I found it to be fo much 


Nitrous Air, ^^ 

phlogifticated, that one meafure of it and 
one of nitrous air occupied the fpace of 
1.92 meafures. 

Upon the whole, it feems that the greater 
effed: of the folution of green vitriol in 
decomposing nitrous air muft be owing to 
the flronger affinity between the fpirit of 
nitre and iron, than- between the fame acid 
and copper or zinc. 

They feem to fhow, however, that there 
is little, if any martial earth in nitrous air, 
at leaf!:, that fueh earth exiiling in nitrous 
air is not combined with phlogifton, or in 
a metallic ftate ; fmce this air is decompofed 
by the nitrous acid in it quitting the 
phlogiflon with v/hich it was already 
combined, in order to unite itfelf to the 
iron in the folution, at the fame time that 
the phlogiflon which entered into the 
nitrous air contributes to blacken the folu- 
tion. It will, perhaps, however be thought 
extraordinary, that the nitrous acid fliould 
have a ftronger affinity with iron than the 
vitriolic, which, on this hypothefis, it 
?ni]fl, in this particular cafe, have. 

E 3 That 

54 Obfervations on 

That the folution of green vitriol was not 
blackened by any peculiar affinity that it 
had with phlogiflon, fo as to decompofe 
the nitrous air by feizing upon it feemed to 
be evident from this, that when I made an 
effervefcence of iron filings and brimftone 
over the folution of green vitriol, there 
was no change of colour produced in it. 
The fame was alfo the cafe when this 
effervefcence was made over the folutions of 
blue and white vitriol, fo that though the 
phlogiflon fet loofe in this procefs was im- 
bibed by the air, and phlogiflicated it, thefe 
folutions were not at all affed:ed by it. 

This effe6t of the folution of vitriol on 
nitrous air helps to explain a phenomenon, 
which I had often obferved v/ithout under- 
ftanding it. When the water in my trough 
had got impregnated with various metallic 
fabflances, that which was contiguous to 
the nitrous air, in jarp ftanding in it, would 
be of a darker colour than the rt^ of t\iQ 
water. This mufl have been in confe- 
quence of the affinity between the fpirit of 
nitre in the nitrous air and the metallic mat^ 


Nitrons Air, ^^ 

ter difTolved in the water, by means of fome 
acid that happened to be mixed with it; 
while the dark colour of th^ water muil 
have been acquired from the phlogifton of 
the nitrous air, partly decompofed by this 
means. At one time, when the water in my 
trough was particularly foul, and feemed dif- 
pofed to make a depofit, I impregnated part 
of it with nitrous air, and the water, by 
this means, prefently became of a darker 
colour than before. 

,Tg determine whether the phenomena 
attending the impregnation of the folution 
of green vitriol with nitrous air depended, 
in any meafure, upon the feeming afirin- 
gency oi that folution, and of chalybeate 
waters, I impregnated a quantity of green 
tea, which is alfo faid to be aftringent, 
with nitrous air, but no fenfible change of 
colour was produced in it. 

In my former publications I have men- 
tioned a variety of circumftances in which 
nitrous air is remarkably diminiflied, in fe- 
verd of which it palTes through a fliate in 
E 4 Avhich 

^6 Ohfervations on 

which a candle burns in it quite naturally, 
and fometimes with a much enlarged flame, 
and at lail becomes mere phlogiflicated air. 
in all thefe procefTes I took it for granted, 
(not having examined the air except when 
it was completely or, at leafl, very nearly 
reduced to one of the two itates above- 
mentioned) that the aproximation to' its 
final ftate of phlogilHcated air was equable, 
fo that as foon as it began to be diminifhed, 
it alfo began to lofe its power of aiFedting 
common air. I find, however, that, with 
refped: to feveral of the caufes of diminu- 
tion, and perhaps all of them, the air 
pafies very fuddenly from the ilate in which 
it is perfed: nitrous air, to the ilate above- 
mentioned^ but that the term at which 
this change takes place is various, as fome-. 
times tv/o thirds, and fometimes fourteen 
fifteenths of any quantity on which the ex^ 
periment is made, will have difappeared 
before any fenfible change can be obferved 
jn the remainder. I have even fometimes 
httVY inclined to think that its powe# of 


Nitrous Air, ^j 

afFedting common air has been rather in- 
creafed than diminifhe J at the beginning of 
thefe procefTes. 

I imagine, therefore, that, as foon as 
either the nitrous acid, or the phlogiilon 
which enters into the compontion of nitrous 
air, is feized upon by any fubftance which,, 
has a Wronger affinity with either of them 
than they have with each other, fo much 
of the other principle as was combined 
with it is precipitated, fo that the air which 
remains is not at all altered from what it 
was, at leaft for a conliderable time. It 
will appear^ however, that the flower the 
procefs is, the greater quantity of nitrous 
air will be preferved in the Hate of phlo- 
gifticated air, and the quicker the procefs, 
the farther it will proceed before this 
change takes place. 

I en'tertained the iirft fufpicion of my 
having been miftaken in my former opi- 
nion (though it is not an opinion that I be- 
lieve is diredly expreifed in any of my 
former publications) vv^hen I was examin- 
ing fome nitrous air in which I had con- 

^8 , Ohfervations on 

fined a fowl, in order to preferve it as long 
as pofTible from putrefadion. For though 
this air was greatly diminiihed in quantity, 
it affecfted common air quite as much as 
the belt nitrous air I had ever tried. 

. Being deiirous of afcertaining this fa(5l 
with abfolute certainty, with refpecft to 
fome one caufe of the diminution of ni- 
trous air, I placed a pot of iron filings and 
brimfione in a jar of nitrous air, and let it 
remain there a whole day, keeping it ge- 
nerally v/arm, near the fire, the ingredients 
not being good of their kind, and not dif- 
pofed to ferment. As the diminution pro-, 
eeeded, I kept taking from it fmall portions 
of the air, by introducing into it a fmall 
jar full of water j which, being emptied 
within the jar, I withdrew, filled with the 
air from within it. Doing this occafion- 
ally, I obferved no change of the quality of 
the air when it was reduced to one third of 
its original bulk, for it retained its full 
power of diminifliing common air. 

The next day I found it dimini/hed to 
one fourth of the whole^ and then a candle 


Nitrous Air, ^59 

burned in it in a manner not to be diflin- 
guifhed from the burning of a candle in 
common air. But it was not common air; 
for it was not at all diminifhed by frefh 
nitrous air, and it afFe(fted common air fo 
little, that one meafure of it and one of 
common air occupied the fpaee of 1.85 
meafures. It had not acquired the peculiar 
property of fixed air, for it did not make 
lime water in the leaft degree turbid, and 
it bore confiderable agitation in water 
without being much diminifhed. 

The diminution of nitrous air by means 
of fpirit of nitre is effed;ed in the fame 
manner ; and as this diminution was made 
more quickly, on this account, perhaps, 
it proceeded much farther before I could 
perceive anychange in it. In one experi- 
ment of this kind, I thought the change 
took place when the air was diminifhed to 
one twelfth of the whole, but in another 
cafe there was no change till it was reduced 
to between one twelfth and an eighteenth 
part, when it was completely phlogifH- 
cated. In this mode of diminution I was 


6q Ohfervations on 

not able to find it in that ftate in which i 
candle could burn i;i it. At another time 
when exadly one fifteenth of the whole 
remained, it aife(5ted common air mani- 
feftly lefs than frefh nitrous airj but here 
again, when only one eighteenth remained 
it had loft all its peculiar property. 

The diminution of nitrous air by the 
folution of green vitriol is effected according 
to the fame rule. I decompofed nitrous air 
l)y expofing it to be abforbed by the folu- 
tion of green vitriol till about one fourth 
of the original quantity remained, but it 
affedled common air as much as it had done 
before any part of it was abforbed. 

Such, alfo, is the manner in whi-ch 
nitrous air is diminifhed in a bladder, as it 
is defcribed in my third volume, p. 151, 
Nitrous air reduced in this manner from 
ten ounce meafures to two and an half, was 
fo much altered, that one meafure of it and 
one of common air occupied the fpace of 
1.75 meafures. It then extinguilhed a candle 
without any appearance of a blue flame. 
When a little more of it was abforbed by 


Nitrous Air, 6i 

the fame procefs, I fouad the remainder all 
phlogifticated air, not affed:ing common air 
in the leaft. Till the nitrous air was re- 
duced, in this manner, to very near one 
fourth it continued unchanged. 

If, however, common air be mixed with 
nitrous air, by which means it becomes in 
part phlogifticated air, the Tpirit of nitre 
will abforb the fuperfluous nitrous air only, 
and confequently leave the remainder more 
diluted with phlogifticated air. I put a 
meafure and a half of common air to twa 
meafures of nitrous air, fo that one meafure 
of this mixture and one of common air 
occupied the fpace of 1.36 meafures. I 
then put fome fpirit of nitre to the mix- 
ture, and when it had abforbed one-diird 
of it, one meafure of it and one of com- 
mon air occupied the fpace of 1.8 mea- 

I alfo introduced a piece of hot charcoal 
into a phial of nitrous air by v/hich means 
one half of it was abforbed, and found that 
the remainder had not lofl its power of 
diminifhing common air in any fenfible 
4 degree. 

62 Qbfervations on 

degree. The abforption of all kinds oi aif 
by charcoal is a very capital difcovefy of the 
Abbe Fontana, which he has been fo oblig- 
ing as to give me leave to mention. 

When nitrous air has been kept a long 
time in w^ater, it is known to be diminished, 
and in this cafe I fufpedt that it lofes its 
virtue gradually, ' being impaired from the 
firft. I have found, however, that by long 
keeping in perfedly ftagnant water, and 
without any change, except to fupply the 
wafte by evaporation, it came to the ilate 
of phlogillicated air -, but by what fteps in 
the progrefs I omitted to obferve, having 
taken it for granted that this was always 

On the nth of November 1773, I filled 
two quart bottles with fr^fh made nitrous 
air, one from iron, and the other from cop* 
per, and then fet them afide, with their 
necks immerfed in jars of water, and never 
agitated the air or the water in contact with 
it, only fupply ing the jars with frelh water 
as I perceived it was wanted. On the 29th 
of September 1778, I examined the ftate of 


Nitrous Air, 6'^ 

thefe bottles of air, and found as follows. 
Of that which had been made from iron 
about one half was abforbed, and of that 
from the copper about a third ; but both 
of them were equally and perfectly phlo- 
gifticated, making no effervefcence with 
common air, and extinguifhing a candle. 
That which had been made from copper 
did not make lime water turbid, and the 
fame, I doubt not, would have been the 
cafe with the other, if it had been tried. I 
did this from a fufpicion, that, fmce fixed 
air may be compofed from the nitrous 
acid, nitrous air, in fome of its changes, 
might, in part, aiTume that form. I had not 
given much attention to thefe bottles of 
air, but I do not think they had been at 
all diminiflied the laft year, or the laft year 
and half. 

I was not able to catch the inflammable 
ftate, as I may call it, of nitrous air in 
dimini{hing it by the eleSlric fpark, nor did 
I attend to the intermediate fliate of it ; 
.but I have made this experiment more at 
large than I had done before, and the par- 

64 Obfervations on 

ticulars may be worth reciting; I nearly 
filled a phial, containing a;bout fix ounce 
meafiires of nitrous air, confined by quick- 
filver j and taking the electric fpark with- 
in it, it was in about aii hour diminilhed 
about one half, but after that very little. 
The quickfilver was much corroded, and 
a candle went out in the remainder of the 
air. The diminution of common air by 
the electric fpark requires a good deal of 
firne, but this procefs goes on very rapidly 
with nitrous air. I repeated the experiment 
in a tube a quarter of an inch in diameter, 
receiving the fpark upon water tinged blue 
with the juice of turnfole; and the dimi- 
nution was fo quick, that the motion of 
the water up the tube was conflantly itVL" 
fible to the eye. The water was deeply and 
permanently red. 

Mr. Bewlys Pyrophorus alfo decompofes 
nitrous air, and prefently reduces it to the 
ilate of phlogifticated air. Having put a 
quantity of it into a glafs jar ftanding in- 
verted in quickfilver, I introduced fome 
§1! nitrous air to it, when the pyrophorus 
wmm' became 

the Nitrous Acid, 6^ 

became inftantly red hot. What remained of 
the nitrous air had no efFed: on common 
air, and extinguifhed a candle. All this 
change was effected at once. For though 
the nitrous air continued in the jar a day 
and two nights after it had been admitted 
to the pyrophorus, there was no farther 
change in its dimenfions. 

The willow plant, as I fhall obferve, ab* 
forbs nitrous air as well as every other kind 
of air. What were the intermediate ftates 
of it I did not note, but when the air was 
reduced to one tenth of its bulk, I found 
it to be mere phlogiflicated air. 


Of the Impregnation of Water with the 
Vapour of nitrous Acid. 

IH AVE obferved that the confequence 
of impregnating water with the vapour 
that efcapes from fpirit of nitre is making 
it fparkle, with the fpontaneous produdion 
of nitrous air. This feems to prove that, 
F unlefs 

66 Obfervations on 

unlefs there be earth in all water, there 
cannot be any earth necelTarily contained in 
nitrous air. But at the time of my former 
publication I had always produced this ap- 
pearance by throwing into the water the red 
nitrous vapour from a violent effervefcence 
of fpirit of nitre and bifmuth i and in this 
violent effervefcence it was poffible that fome 
of the earth of the metal might be carried 
over, as fome of the water evidently was. 
I was, therefore, now careful to avoid this 
objedtion, which I did by expoling a phial 
of pure nitrous acid to nitrous air over the 
pureft diftilled water. This I did by means 
of a tube with a ground ftopper at each 
end. For by flopping and unftopping them 
alternately, I could eafily manage fo as to 
place the phial of fpirit of nitre, fupported 
by a thin glafs tube, very near the top of 
the veffel, then fill it quite to the edge of 
the veffel with water, and after that dif- 
place the water by introducing nitrous air. 
As the nitrous air was abforbed I introduced 
more, by means of a bladder previoufly 
filled with it. The quantity of common 


the Nitrous Acid. 6y 

air above the fpirit of nitre was quite 
trifling in proportion to the bulk of 
the tube. 

In thefe circumftances I obferved that 
when the nitrous acid became blue, and 
hardly before, the water next to it begaa 
to emit bubbles of air. To the formation 
of this air (which was doubtlefs nitrous air) 
nothing could contribute but the effluvia 
of the nitrous acid, and fomething that the 
water itfelf might furnifh -, and this water 
had been flowly and carefully diftilled in 
glafs velTels. 

The quantity of water ufed in this ex- 
periment was about four ounce meafures, 
and the quantity of nitrous air abforbed was 
about fifteen or twenty ounce meafures ; 
the circumflances of the experiment being 
fuch that very little more could have been 
abforbed without changing the acid. I 
then carefully diftilled the v/ater, which 
had imbibed v/hatever had been precipitated 
from the decompofed nitrous air, and found 
a pretty large earthy fediment, covering a 
fpace at the bottom of a retort of about an 
F 2 inch 

68 Ol?fe7"uations on 

inch and a quarter in diameter, befid^s 
having made a great number of white fpecks 
at a conliderable diftance from that central 
fpot. This matter was generally white, 
but where it was thickefl it was llightly 
orange coloured. Spirit of fait diflblved 
the whole of this earthy matter, and be- 
came of a deep orange colour in confequencc 
of it. This might feem to be earth which 
had been precipitated from the nitrous air, 
and perhaps fome of it might have been 
thus produced; but when I afterwards 
evaporated to drynefs the fame quantity 
of the fame diflilled water I found a larger 
earthy fediment than I had expe(3:ed ; and 
though I think not fo much as that above 
defcribed, yet enough to make me hefitats 
m drawing a general conclufion from it. 

t E C^ 

%^if rolls Air* 69 


Attempts to preferve animal Suhflances in 
nitrous Air, 

IT was among my earliefl obfervations 
on nitrous air, that animal fubftances 
would not putrefy in it. I have lince my 
laft publication made a few experiments, 
in order to afcertain whether it be poffible 
to derive any advantage from this property 
of nitrous air for culinary purpofes. But I 
cannot fay that my obfervations have been 
very favourable to it in this refpedr. 
Nitrous air will, indeed, preferve flefh 
meat from putrefaction; but after long 
keeping in this manner it becomes very 
oiFenfive, both to the noftrils, and the 
palate, though the fmell is not altogether that 
of putrefad:ion ; and indeed the fubftance 
continuing quite firm, it could not be pro^ 
perly putrid. Though thefe experiments were 
not quite fair, becaufe the nitrous air had 
not been renewed fo often as it ought to 
F 3 h.2iVZ 

^o O'hfervations m 

have been, feveral of the phenomena may. 

be worth mentioning. 

On the 28 th of April 1777, I put two 
pigeons into two jars of nitrous air, juft 
wide enough to contain them, with about 
as much nitrous air in the jars, as the bulk 
of the pigeons. From this time till the 
4th of June following I had renewed the 
nitrous air but once, and then, taking them 
out, I found them both free from all fmell 
of putrefadiion. One of them was broiled, 
when the flefh was found to be fweet, but 
it had not the natural tafle of the pigeon, 
and was, on the whole, unpleafant. The 
fielh was quite red throughout, and a little 
harder than that of a pigeon generally is. 
The water contained in the cups, in which 
the jars with the pigeons had flood, had 
generally been very ofFenlive, fo that it 
fiiould feem that the putrid effluvium (con- 
taining, probably, much phlogifton, and 
perhaps the mofl nutritive part of the flelh) 
had pafTed through the nitrous air, and th© 
water, into the furrounding atmoiphere. 

2 I re-. 

Nitrous Air, ji 

I replaced the pigeon that was not ufed, 
and let it remain, along with two others 
which had been kept the fame time, till 
the 13th of September following, in all, 
near fix months, or the whole fummer 
feafon -, but I had not been careful to change 
the air very often, though I did it two 
days before I took them out the laft time. 
The pigeons had now certainly a very bad 
fmell, though their fleih was firm, and fo 
were even the bowels of one of them which 
had not been drawn. When they were 
drelTed, they were much more offenfive, 
and had a ilrong fmell of putrefaction or 
fomething very much refembling it. The 
flefh was red throughout, flill firm, and 
exclufive of the fmell, had little or no tafte. 1 
My friend, Mr. Magellan, who was with 
me at the preparation of them, had not fo 
bad an opinion of this piece of cookery 
as I had. 

On the loth of May I put into a jar of 

nitrous air a large wood-pigeon ; and taking 

it out on the i8th of June following, ob- 

ferved that it had a Ilrong and ofFenfive 

F 4 fmellj 

72 O.hfervations on 

fmell, but the fiefh was perfectly firm. 
Though a very great part of the air had 
been abforbed, and during the fortnight 
preceding the examination it had not been 
fupplied with frefh air, as it had been 
occafionally before, the air to which it had 
been expofed all that time diminifhed com- 
mon air quite as much as frefh made nitrous 
air. It v/as this obfervation that gave me 
the firft fufpicion of the manner in which 
nitrous air is diminifhed in this and in other 
procelTes, Having replaced the pigeon in 
the jar, I found on the 7th of AugulT: fol- 
lowing, that the air was but flightly 
nitrous, and on the 22d of the fame month 
it was mere phlogifticated air. After this 
I negleded to attend to it, and at lafl threw 
it away. Whether, in this procefs, the 
nitrous air ever comes into a ilate in which a 
candle will burn in it, or not, I cannot 
tell. The experiment is a very unpleafant 
one, and I {hall hardly repeat it. 

In all thefe cafes the ileih was kept a 
long time, viz. through the iix fummer 
months 5 and though nitrous air failed to 


Nitrous Air. ^^ 

"l^referve meat in a flate fit for eating fo 
very long, it may poflibly anfwer the pur- 
pofe for a few days tolerably well, as it 
will certainly reftore meat that has begun 
to turn putrid. One trial of this kind I 
did make. [ 

On the 14th of June 1777, I took a fowl 
which had been killed a week, and which 
had been purpofely kept till it was oiFen* 
five; and putting it into a jar of nitrous 
air, obferved that the air began immediately 
to be abforbed, and on the i6th I took the 
fowl out, when it had no fmell of putre- 
facftion at all j but when it was boiled, 
.though myfelf and feveral other perfonfi 
tailed of it, and perceived nothing difagree- 
able in the tafte itfelf, we were difgufted 
with a faint fmell that came from the body 
of the fowl, when we held it to our noftrils. 
Perhaps it had not been expofed to the 
nitrous air quite long enough. 

Though part of this air had been ab- 
forbed, the remainder diminifhed common 
air quite as much as any freih made 
nitrous air. 


^4 Ohfervathns on 

On the fubjed of this fedion I fhal! 
obferve that Dr. Millman having been fo 
obliging as to inform me that he had found 
that bile is prevented from becoming putrid 
much longer by being impregnated with 
fixed air, than it could otherwife be^ I 
was dejSrQus pf trying what efFed: the im- 
pregnation with nitrous air would have 
upon it. Accordingly, on the 19th of 
February 1777, I impregnated a quantity 
of ox bile, with which he fupplied me, 
with nitrous air 5 when, from being vifcid, 
it prefently became limpid like water, and 
alTumed a brownifh hue, without deport- 
ing any thing that I could perceive. This 
bile continued perfedly fweet till the 20th 
of March following, when it was packed 
up, along with other things, and removed 
<from London into the country. Examin- 
ing it fome time afterwards, I found it 
had contraded a fmell of putrefadion, and 
on the 23d of April, it was quite putrid. 
The fame brown colour continued, but it 
had depofited fomething of a whitifli 


Nitrous Ah'. 75 


Mifcellaneous Experiments relating to nitrous 

L •'^LIVE oil, by which a quantity of 
V-^ nitrous air had been confined in a 
phial feveral months, had abforbed almoft 
the whole pf it, and that part of the oil 
which was contiguous to the air was coa- 
gulated in lumps, as if it had been frozen, 
find remained a long time at the top of the 
oil. But afterwards, being loofened, I fup- 
pofe, by the warmth of the weather, it all 
funk to the bottom, as the ice of oil always 

II. I rather fufpecfl that when nitrous 
air is mixed with common air, in a greater 
proportion than is requilite to the complete 
iaturation of the common air with phlo- 
gifton, the fuperfluous nitrous air is more 
difpofed to be abforbed by water than pure 
nitrous air. It appears, however, that, in 
no great length of time, fuch mixtures are 
brought to the fame dimenfions as if only 


y6 Obfervations on 

half the quantity of nitrous air had been mix- 
ed with the common air. This, I think, may 
be inferred from an experiment which I 
made to try the difference between old and 
frejh made nitrous air, both having been 
made in the fame manner, and, I believe, 
having been originally of equal ftrength. 

Odlober 25, 1777, I mixed equal quan-« 
titles of the fame common air with equal 
quantities of the old and frelh made nitrous, 
air. What fpace they occupied at that 
time, and in feveral fubfequent periods, is 
ireprefented at one view, as follows : 

With the old nitrous air. With the new, 

Od:. 27,1777. 1.22 1.05 

Nov. 10, 1.07 0.93 

24, 0.96 0.86 

Feb. 2, 1778. 0.84 0.8 

The laft is one fifth lefs than the original 
bulk of the common air, and confequently 
very near to the utmoft limit of the dimi- 
nution of common air by any proper phlo- 
giflic procefs. An accident prevented my 
obferving this progrefs any farther. 


i^itrous Air. y,7 

III. I found, very unexpededly, that a 
confiderable difference would be made in 
the dimenfions of the mixture of air by a 
circumftance in the manner of mixing them 
that one would not readily fufped:, and I 
am not able to account for it. My ufual 
method, as I have obferved in the Introduc- 
tion, has been to mix equal meafures of 
nitrous and common air in a low jar, and 
then to transfer the air into a graduated 
tube, three or four feet long. What I 
obferved is, that I could make a difference 
of five hundred parts of a meafure by making 
the air run up the long tube quickly or 
llowly. The more ilowly it afcended^ the 
lefs fpace it occupied. To afcertain whe- 
ther it depended merely upon the two 
kinds of air being fo much longer together 
in the wider velTel, or in the funnel through 
which it was poured into the tube, I made 
the mixtures over night, and transferred 
them into the graduated tube the next 
morning, but I flill found the fame diiFer- 
ence, depending upon the circumftance 

yS Obfervation^ on 


Of the Colour of the Marine Acid, 

L L the chemiils, as far as I can find, 
who have written on the fubjed: of 
the marine acid, fpeak of its colour ^ as of a 
thing eiiential to it, and never fail to de- 
fcribe this as a neceflary part of its defini- 
tion : " Thus Mr. Macquer, in his JDiSlio- 
nary, fays, that this acid differs from the 
vitriolic in h.'xvmg fmell and colour J" He 
alfo fays, it differs from the nitrous acid by 
its colour, '* which is more yellow and lefs 

In the experiments of which I gave an 
account, in my third volume, I gave a 
good deal of attention to this fubjedt, but 
at that time I had not been able to afcertain 
•on what it is that the colour of this acid 
depends. Sometimes, I there obferved, I 
had procured it quite colourlefs, efpecially 
when I made it by impregnating water 
wdth marine acid air, but at other times I 
was not able, though I endeavoured to do 


the Marine Acid, yq 

it, to procure it without colour. I have 
-lince, however, perfe(Stly fatisiied myfelf 
with refped: to the colour of this acid, and 
can at any time make it as colourlefs as water 
itfelf, the colour always coming from fome 
impregnation, generally, if not always, of 
fome earthy jnatter , with almofl every thing 
of which kind it unites, and from which 
it generally takes fome colour or other. I 
can alfo inflantly difcharge any colour that 
this acid has acquired, and refliore it again 
at pleafure, as will appear in the courfe of 
thefe obfervations. 

As I always make my own fpirit of fait, 
as well as my fpirit of nitre, and was fatis- 
fied, from my former obfervations, that 
colour is not effential to this acid, any 
more than to the nitrous, or the vitriolic ; 
on the firft of Augufl 1777, having occa- 
fion for a quantity of fpirit of fait, I was 
determined to make the diftillation with all 
the attention that I could give to it, taking 
the produce at different times, which is 
my general cuftom, and which has been 
the occalion of my making a variety of in>- 


8o Obfer^atiom on 

portant obfervations. I alfo received the fu- 
perfluous vapour, or marine acid air, with 
the fame precautions, and in the fame man- 
ner. The apparatus was nearly the fame 
with that of which a drawing is given in 
the plate to my third volume. Fig. 4. The 
retort only being much larger, and ufing 
phials with water inflead of the cup g. In 
this prpcefs alfo I feldom make ufe of any 

Every thing being thus prepared, and 
having luted the veffels with a mixture of 
clay and fine fand, I began the diftillation ; 
and obferved that the firft produce was ftraw 
coloured, as ufual ; but all that came after- 
wards was quite colourlefs, like water. 
Alfo, all the impregnations of the Water 
with the fuperfluous vapour were colour- 
lefs. But the heat happening to abate to- 
wards the end of the procefs, a quantity of 
water rufhed fuddenly from the phial that 
received the impregnation, through the re- 
ceiver, into the phial that contained the 
diftilled acid; when all the acid that was 
in it, which was then quite colourlefs, 


the Marine Acid. 8l 

immediately aflumed as deep a ilraw colour, 
as that of the firft produce of the diftUla- 

This procefs might have been fufficient 
to explain to me the whole myftery of the 
colouring of the ipirit of fait -, but it did 
not, and all the real advantage I gained by 
it was having in my poflellion a large quan- 
tity of pure colourlefs fpirit of fait, to 
which I might endeavour to give colour in 
future experiments. For all the hypothelis 
that occurred to me from confidering the 
phenomena of this procefs was, that the 
colouring of this acid, as in moil other 
cafes, and efpecially in fpirit of nitre, was 
ov/ing to heat, or phlogijion ; fo that I was 
milled by the general maxims of the 
chemifhs, and alfo by the analogy of the 
two acids, and, indeed, that of the vitri- 
, olic acid alfo, which is known to acquire 
its black colour from fubflances containing 

Thus I coniidered the colour of the firft 
produce of fpirit of fait, in the above-men- 
mentioned procefs, as fimilar to the ufual 
G colour 

§2 Obfervations on 

colour of the firft produce in the diftilktion 
of fpirit of nitre, mz. to ibme unobferved 
phlogiftic matter in the materials -, and I 
confidered the deep flraw colour at the 
laft, as occafioned, likewife, by fome phlo- 
giftic matter driven into the veffel by the 
fudden rufliing in of the water. Befides, I 
had more than once found fpirit of nitre to 
become inftantly of a deep green by a 
Similar rufhing of water into the recipient. 

Conceiving that it mufl: be phlogiflon that 
gave colour to this acid; as well as to the 
nitrous acid and the vitriolic, I imagined I 
had nothing to do but to difcover the proper 
mode of combining them ; and I made trial 
of feveral things for that purpofe, as put- 
ting into the colourlefs acid bits of char- 
coalj quenching hot charcoal in it, and 
mixing with it various other fubfbances 
containing phlogiflon, both hot and cold, 
but all without any effedt. 

As I had given colour to fpirit of nitre 
by m.erely heating it in glafs tubes her- 
metically fealed, I fubmitted the fpirit of 
fait to the fame trial 3 and for fome time 


the Marine Add, 83 

Imagined that I had fucceeded. For, in 
feveral inftances, the fpirit of fait did be- 
come coloured in thefe circumftances. 

About half an ounce meafure of colour- 
lefs fpirit of fait being confined in a glafs 
tube an inch in diameter, and three feet 
long, hermetically fealed, on being ex- 
pofed to heat, prefently affumed the deepeft 
ufual ■ colour of fpirit of fait. Sufpedting 
that there might have been fome unper- 
ceived bit of ftraw, or fome fuch thing in 
the large tube, I took a fmall one that was 
perfedily clean -, and preparing it in the 
fame manner, I expofed it to the heat of a 
common fire, and with the very fame refult. 
The acid had acquired a perfect ftraw co- 

But I was more confirmed in my opinion 
that it was heat, or phlogijfton, or both, 
that produced this effect by finding that I 
got a peculiarly deep ftraw colour when I 
had inclofed the fpirit of fait in a tube in 
which fome oil had been before expofed to 
heat in the fame manner, and to which a 
little of it adhered: and, what I had not 
G 2 much 

84 Obfervations on 

much attended to before, I now obferved 
that the acid retained this ftraw colour 
when it was quite cold. But, notwith« 
{landing thefe promifing appearances, rny 
hypothecs was totally overturned by 
finding, a day or two afterwards, that when 
I had expofed two glafs tubes, in all re- 
fped:s, as nearly as I could judge, alike, 
containing the fame colourlefs fpirit of fait, 
to the fame fire, and the fame length of 
time, only one of them acquired the ilraw 
colour, while the other continued colour- 
lefs, as at firft. I examined both thefe 
tubes with the greateft attention, but could 
not difcover any caufe of this difference* 
There was indeed, more of the earthy 
matter, of which I (liall treat prcfently, 
in the tube in which the acid was co- 
loured, but that in which the acid con-^ 
tinned colourlefs had a fmall crack in it, out 
of which fome of the acid had oozed, fo 
that I did not attribute this difference of 
colour to that circumflance. 

At length, on the 6 th of September, I 
difcovefed, by the mereft accident, the 


the Marine Acid, 85 

whole myftery of what I had been fo long, 
and fo intently inveftigating. For, having 
fome other ufe for the phial which con- 
tained the fpirit of fait, I poured it into 
another phial, in which there had formerly 
been fome iron filings and water, and the 
fides of which had a flight incruftation of 
ochre, which is known to give to glafs a 
tinge that is not eafily got ou| : but the 
moment that the colourlefs fpirit of fait 
touched this red incruftation, it became of 
a deep flraw colour, and the phial where- 
ever it had been touched by the acid, was 
perfedtly clean. 

After this it was impoflible not to con- 
clude that the colour of fpirit of fait is not 
owing to phlogiflic matter, like the colour 
of oil of vitriol, or that of fpirit of nitre, 
but to an impregnation of fome earthy 
matter, with which it is known readily to 
unite i and farther obfervations prefently 
placed this hypothefis beyond all poffible 
doubt. I was now alfo fatisfied, that 
the firft produce of fpirit of fait, in the 
procefs above-mentioned, mufl have touch- 
G 3 ed 

S6 Ohfer '[Rations on 

ed fome of the clay, or fand, with whiclr 
the vefTels had been luted, and that the 
water, in its violently rufhing into the re- 
ceiver, mufl have met with more of it, 
though at that time, fufpeding nothing of 
this, I did i;iot perceive it. 


Of the Impregnation of Marine Acid with 
'various earthy Subjiances. 

"AVING now difcovered the power of 
the marine acid to diflblve earths, I 
was dejfirous of examining the circumftances 
attending various folutions of this kind, 
both with refped: to the earths themfelves, 
and the colour of the faturated acid. 

Spirit of fait dilTolves a great quantity of 
rufi of iron with efFervefcence, but not with 
much heat. The mixture was' of a very 
deep brown, and what was not diiTolved 
was of a dirty blackifh colour. But pof- 
fibly this might be owing to the rufl of 
iron not being perfedly free from all 


the Marine Acid. Sj 

foreign matters. The fpirit of fait thus 
faturated with the ruft of iron diifqlved 
iron filings, and produced inflammable air; 
after which it was green. Having faturated 
a quantity of fpirit of fait with the ruft of 
iron, I evaporated it to drynefs, when all 
the fluid part was difperfed in colourlefg 
fumes, and the ochre was left behind, and 
was .rediflblved by frefli fpirit of fait. I 
would obferve, by the way, that fpirit of 
fait is of excellent ufe to clean glafs vefl^els 
tinged with the rufl; of iron, and many 
other matters. This may poffibly have 
been known to others. To me the obfer- 
vation was cafual, but of great value. 

This acid diflblved a large quantity of 
floivers of zinc with great heat and ejffervef- 
cence. During the folution the acid be- 
came of a turbid black colour, but when it 
flood to fubfide, the black matter floating in 
it was depofited upon a mixture of black 
and white matter at the bottom of the 
phial, and the faturated acid was quite 
colourlefs, exadly like water. Alfo when I 
put flowers of zinc to fpirit of fait deeply 
G A coloured 

88 Obfervations on 

coloured with the ruft of iron, the acid be- 
came colourlefs again. 

Minium became white by the affufion of 
the fpirit of fait, which acquired from it a 
beautiful yellow colour. A great quantity 
of it was diflblved, though more of it re- 
mained undiffolved than of the flowers of 
zinc. When the red colour of the minium 
was quite difcharged, frefh fpirit of ialt,- 
though it diflblved, and became faturated 
with the white minium, acquired no 
colour from it. 

When I had frequently waflied a large 
quantity of minium in fpirit of fait, 
(though not till no more of it would have, 
been diffolved) I put it into a green glafs 
retort, and expoflng it to as much heat as 
the glafs would bear, I got from it hardly 
any fixed air, but about as much dephlo- 
gillicated air as I imagine it would have 
yielded before any fpirit of fait had been ap- 
plied to it. It feems, therefore, that the 
fpirit of fait diilodges from the minium all 
the fixed air it contains, but has no power 
of afFedling its property of yielding dephlo- 


the Marine Acid. go 

gifticated air. The matter melted into a 
red fluid fubftance, which, when cold, ex- 
panded, and broke the retort. This refi- 
duum gave a yellow tinge to fpirit of 

Spirit of fait diflblved a great quantity of 
red precipitate, with great heat, but with- 
out efFervefcence. During the folution the 
acid was of a turbid white colour, and the 
precipitate is generally black, though fome 
parts of it continued red till they were 
quite diffolved. But what remained un- 
diffolved at the lafl was all black. After it 
had fubfided, all the opake matter was de- 
pofited, and the acid was beautifully tranf- 

This acid dillblves a great quantity of 
lapis caliminaris, but not the whole of any 
part of it. The folution is made without 
heat, and it leaves no colour whatever in 
the fpirit of fait. 

Spirit of fait had no efFe6l whatever on 
crude antimony, on wolfram, calcined or un- 
calcined, or on white arfenic. It is not 
affeded by vermilion immediately ; but in 


go Obfervations on 

time it acquires from it a delicate yellow 
colour. It has alfo no feniible immediate, 
eifed: on the black powder into which 
mercury is converted; but when lead i& 
mixed with it, it, in time, acquires a deep 
orange colour from it. This muft be pro- 
duced by its feparating the calx of lead 
from the fuperphlogillicated mercury, with 
which it is mixed. 

All the above-mentioned folutions are 
thofe of metallic earths, or other metallic 
matters, in fpirit of fait. The following 
obfervations relate to the folution of 
earthy fubftances of a different kind in the 
lame acid. 

Colourlefs ipirit of fait diffolves com^ 

pletely a great quantity of very white lime, 

and is then of a ftraw colour ; and the fame 

was the effed: of the folution of a pure 

liriie from oyiler fhells. It alfo diifolved as 

much lime of a common fort, and was then 

of a true orange colour. But this feemed 

to be owing to a brownifh matter in the 

lime, which was probably fome earth of 

Jron that was contained in it. At the fame 


the Marine Acid, gj. 

time I obferved that lime wa^ not fenfibly 
aiFedied either by oil of vitriol, or fpirit of 

This acid diflblves a large quantity of 
calcined magnejiay and is then of a ftraw 

It does not fenlibly aiFedti^//^, but when 
it was confined in a glafs tube hermetically 
fealed, with a quantity of founded glafs^ 
and expofed to a boiling heat, the glafs. 
feemed to be a good deal dilTolved, and the 
acid became of a ftraw colour. 

From pipe clay fpirit of fait acquires a 
delicate yellow colour. 

Wood ajhes, out of which air had been 
expelled by heat, were dilTolved in fpirit of 
fait, and became black, but the colour of 
the acid was not changed. 

The following fubftances were not fen- 
fibly affected by fpirit of fait, viz. plaifter of 
Paris, ileatites, flint, zeolyte, fluor cruft, 
Mofcovy talck, cream of tartar, fedative 
fait, or borax. It had alfo no eifed: on the 
black matter that remains in the retort after 
the procefs for making ether. 


gz OUfervations on 

' It appears to mc that it might be of con- 
liderable importance to the advancement 
of chemical knowledge to go through with 
the examination of all earthy fubftances in 
this manner, afcertaining whether they be 
foluble or infoluble in fpirit of fait, and 
noting all the phenomena refpedting either 
the earths themfelves, or the acid, and 
comparing the refults with the eifecfls of 
other acids, &c. on the fame earths. If 
any thing of this kind be done, at leaft to 
much extent, it is unknown to me. 


Of the Effe£i of a continued Heat on Spi- 
rit of Salt in Glafs T^ubes hermetically 

HAVING made thefe folutions of ear- 
thy matters in fpirit of fait, I expofed 
feveral of the faturated folutions, and other 
things into which the marine acid enters 
to a continued heat, and noted feveral re- 
markable effedts of that procefs. But 


the Marine Add. g^ 

before I relate any of them, it will be pro- 
per to give an account of the treating of pure 
fpirit of fait in the fame manner, bclides 
what has been faid of this procefs in a 
former fedtion. In general, the fpirit of 
fait, expofed to heat in glafs tubes herme- 
tically fealed, is enabled to do what it i& 
incapable of in other circumftances, viz. 
to diflblve the glafs itfelf, and more ealily 
to feize upon metallic matters, as the calx 
of lead, and therewith to form a concrete 
fubftance, into which the acid itfelf enters. 
On the 30th of Augufl 1777, I expofe4 
to a boiling heat, in a glafs tube about 
four feet long, and one third of an inch in 
diameter, as much ipirit of fait as mea- 
fured in the tube about an inch in lengtli, 
and kept it boiling about two hours. After 
this the acid was ilill quite tranfparent, and 
the quantity not fenfibly changed, but I 
obferved that there was formed, as it 
cooled, a nurnber of fmall cryflals, perfeiflly 
white, at the bottom of the acid, and adr 
laering to the fides of the tube. When I 
jnelted the end of the tube with a blow 
« pipe 

gs^ Obfervations on 

pipe, the preflure of the atmofphere forced 
the glafs inwards. From this it was evi- 
dent that there had been a decreafe of 
elaftic matter within the glafs, which muft 
have been produced by the incorporation 
of the acid vapour in the cryflals that I 
liave mentioned : for had it been a mere 
•abrafion of the glafs, befides that it would 
have been a powdery fubilance, and not in 
a concrete mafs, the acid vapour would 
have been fet loofe by the heat, and there- 
fore would have prelTed the foftened glafs 

Making ufe of a tube an inch wide, and 
putting into it half an ounce meafure of 
tranfparent fpirit of fait, the cryftals be- 
gan to be formed in about an hour above 
the furface of the acid, and coated the tube 
about three inches, but all of it on the 
upper fide, the tube having been placed in 
an inclined poiition. 

When I expofed to the fame heat the two 
tubes mentioned before, in one of which 
the acid was coloured and the other not, 

I obferved that more of this folid matter 


the Marine Acid, ^^ 

was formed in the former than in the latter, 
the acid having become coloured by dif- 
iblving the glafs. 

When- any of thefe tubes happened to be 
cracked in the procefs, which was fre- 
quently the cafe, there was always a con- 
iiderable incruftation formed on the outfide 
of the glafs, fpreading from the crack, 
out of which the acid had cfcaped. 

Having obferved that, in proportion as 
this earthy, or rather faline matter was 
formed, the acid was diminifhed ; to try 
whether there was any difference in the 
acid that remained from what it had been, 
I took it out of the tube in which it had 
been expofed to the heat, and expofed it 
again in a frefh tube; but I found that 
more faline matter was formed in this tube, 
exactly as in the former.* I repeated the 
fame procefs on the acid that remained in 
the fecond tube, by putting it into a third, 
when more faline matter was produced ; and 
this I Repeated till very little liquid acid 
remained, though the tube broke, and a 



9 6 Obfervdtions oh 

little remaining acid efcaped, before I had 
quite finiihed my procefs upon it. 

At length, however, I completely eiFedled 
what I had been in purfuit of. For I 
cxpofed a quantity of acid in this manner 
till nothing liquid remained in the tube. 
This acid was diftilled water impregnated 
with marine acid air, the quantity was 
about half an inch in length, in a glafs 
tube a quarter of an inch in diameter. 
The lower part of the tube had a thick 
incrullation of white matter, and no more 
moiflure remained within it, than what 
adhered to the fides of the tube, and would 
not run down it. 

Though the acid continued to the laft to 
dilTolve the glafs, it was evidently weakened 
by the continuance of this procefs, fo that 
though both the marine acid air, and the 
water with which it was incorporated, had 
entered into the compofition of the faline 
matter formed within the tube, there was 
in it more of the acid than of the water. 
Having extracted a confiderable quantity of 
this faline matter from one of thefe tubes, 

I took 

the Marine Acid, 97 

f took out the remaining acid, ind frotti a 
pMtn meafure of it, diluted with water, 
and bits of iron, t got three ounce meafures 
of inflammable air ; whereas from the fame 
quantity of the fame original fpirit of fait I 
got, in the fame circumftances 4. i ouiice 
meafures. Allowance, however, mull be 
made for the vapour that had efaped in 
pouring the acid into the tube, and out of 
it again. 

In order to get a quantity 6f this 
faline matter, I kept a large tube with 
about an ounce meafure of fpirit of fait in 
the fand furnace near three months, and 
fucceeded pretty well. It was all formed 
in or near the furface of the acid. The 
heat had been very moderate. For great 
care muft be taken left the glafs fhould 
burft in this procefs. It feems, however, 
that when the heat is more conliderable, 
the hotter acid may difTolve the concreted 
faline matter that it comes into contadl 
with, as appears in the following experi- 

Having expofed 2dwts. of colourlefs 

fpirit of fait, in a long tube, about one 

H ^ third 

'9^ ObfervatioJis' on 

third of an inch in diameter, the tube w^S 
prefently incrufted about the length of 
.kine inches^ with the faline matter, but 
^yery thin ; and I obferved that there was 
none of it within an inch of the furface of 
the fluid. Then making it boil more vio- 
lently, I obferved that whenever the hot 
acid reached the incruftation, it diifolved 
it,; and wallied the glafs quite clean. By 
this means all the incruftation was prefently 
.waftied off, and while the acid continued 
to boil, it did not appear again. 

The reafon why this incruftation was gene- 
rally made at, or rather above the furface of 
.the boiling acid, feems to be, that the acid 
was there the moft concentrated, on its 
expullion from the water ; and this made 
a ftriking difference between thefe experi- 
ments, made with fpirit of fait, and fome 
which I made with water in the fame 
manner. For when I bent the tubes at 
each end, and expelled the liquors by heat 
from one end of the tubes to the other 
alternately, I obferved that with the fpirit 
of fait the incruftations were always made 
2 abova 

the Marine Acid, 90 

aBbve the furface of the boiling liquor; 
whereas, in the tubes which contained 
water only, the inCruftations were always 
made at the place from which the water 
laft evaporated* 

That the fpirit of fait, in thefe expefi- 
mentSj diiTolves the glafs, and efpecially 
the lead that was in it, appeared from the 
following obfervation, which was firft made 
by -Mr, Magellan, who happened to be 
with me at the time* We had wafhed a 
quantity of this earthy, or faline matter, 
in diflilled water 5 when he obferved that 
the water had the taflie oi faccharum Saturni, 
and when the water that had been ufed in 
this manner was mixed with pump water, 
it turned it white, a manifeft proof of its ■ 
containing a folution of lead. 

Spirit of fait not only dilTolved this mat- 
ter when it v/as hot, but alfo a confiderable 
proportion of it when it was cold. When 
I had wafhed a quantity of it frequently 
with diftilled water, till it was quite in- 
fipid, it was not at all affedied by oil of 
vitriol, or fpirit of nitre; but when I had 
H 2 poured 

loo Ohfervations an 

poured upoii it fome fpirit of falt> and let 
them continue together a whole day, three 
grains o£.-k were reduced to a grain and a 
half J fo that half of it was difTolved by 
the fpirit of fait, and the acid acquired a 
deep orange colour. As all the fajine mat- 
ter had been wa,fhed out of this fubftance 
by the water, what remained muft have 
been the earth of the glafs reduced, ta^a 
powdery form,* prdper for the fpirit of 
fait to a^/upon. 

There was an incruflation of whitiih 
matter when I made thele experiments in 
the green or the black bottle glafs, which 
has no lead in it, but it is manifeilly of a 
different nature from that which is formed 
in the flint glafs. The quantity is much 
lefs, and it differs from the other in feveral 
refpe(5ts. When I dipped a large piece of 
a glafs tube, completely covered with this 
incruftation, and which was perfed:ly white, 
in frefh fpirit of fait, it prefently difap- 
peared, as if the acid had diffolved it all at 
once 5 and the incruftation feemed to im- 
bibe the acid, as a wet fpunge imbibes 


the Marine Acid. ioi 

water:- for- when the lower part of it was 
dipped in the. acid, it preifently afcended, 
and moiftened the upper part. But when 
I took this tube out of the acid, .and dried 
it in the open air, the incruflation re-ap- 
peared, exad:ly as at firft. Alfo the acid 
in which it had been long plunged was 
not tinged by it, or only in the fmallefl 
decree imaginable. 

This incruflation alfo adhered much more 
firmly to the green glafs than to the flint, 
and when it was fcraped off with the point 
of a knife, though it left the glafs tranfparent, 
it was not quite fo well polifhed as before : 
fo that, probably, the glafs had been, as 
it were, abraded, the texture being broken, 
but not fo much as to make it feparate 
from the tube, 

I fhall in this place mention an experi- 
ment fimilar to thofe above on the marine 
acid air itfelf, I buried a flint glafs tube 
filled with this kind of air \^ hot fand, 
and let it continue there fome weeks. 
When I took it out, it was covered with 
^ white incruftation. I broke the end of 
H 3 the 

102 Ohfervaftms oji 

the tube under quickfilver, and found that 
feven eights of the whole quantity had been 
abforbed, and water imbibed about half the 
remainder. The very little that was left 
was phlogifticated air. This tube had been 
filled with fo much care, that I cannot 
think there had been any common air 
in it. 

I have feveral times repeated this experi- 
ment, and find that no great degree of heat 
i? requifite to convert the marine acid air 
into this white fubftance. It is not at aU 
^ffeded by fpirit of fait. 


the Marine Acid^ 103 


Of the EiXpofure of various Subjlances con-^ 
taining Spirit of ^ alt to a continued If eat. 

SOME of the phenomena that attended 
the expofure of faturated folutions of 
fpirit of fait to a long continued heat were 
not a little remarkable. 

Spirit of fait faturated with the rujl of 
iron did not boil fo foon as pure fpirit of 
fait, in equal tubes, both hermetically feal- 
ed, which muft be underftood to be the 
cafe in all thefe experiments. In four or 
five hours a white incruftation' was formed 
on the fides of the glafs, after which the 
liquor was lefs vifcid, arid boiled more 
freely than before. - 

Letting it ftand to cool in the night, the 
next day the tube, having lain in an hori- 
zontal polition, was almoft covered with 
fmall incruftations, flightly adhering to it, 
having been depofited from the liquor. The 
tube being replaced near the fire, all the 
concretions difappeared to a confiderable 
H 4 diflancG 

104- Qbjervatims on 

from the end of the tube to which the heat 
was applied, thqfe next to the bottom 
being perfedily white, while the reft were 
brown, the colour of the faturated acid. 
The reaferi ©f thefe various phenomena I 
do not clearly under ftand. 

Spirit c^f . f^lt faturated with red precipi- 
tate, QX w\Xh Jlowers of -■zinc y expofed to 
heat in the fame manner, and at the fame 
time with the folution of the ruft of iron, 
underwent no vilible change whatever, and 
no incruflation was formed withirt-the glafs 
tubes in which they were contained. 

Thefe experiments were made before a 
common fire, and the heat was not applied 
longer than a few hours two or three dif- 
ferent times. The expofure of the fame 
fubflances in a fand furnace for a longer 
time produced a greater effedt. 

The red precipitate in fpirit of fait, 
which had been expofed to this heat three 
or four days, was ftill colourlefs j but from 
the top of the tube, to about the middle, 
on the fide to which it had been inclined, 
it was covered with beautiful white cryf- 


the Marine Acid. 105 

tals, confifting of many fine fpiculae like 
hairs. There was alfo a fmall white incruf- 
tation on the oppofite fide, juft aboye the 
furface of the acid. 

This experiment was made on the 30th 
of September. Examining the tube that 
contained this faturated folution of red pre- 
cipitate on the 19th of January following, 
I found that when it was cold, the whole 
was perfedily folid, and white. With a 
little heat it became liquid, and tranfparent, 
as at the firfl:, but in the cold it was always 
folid. In this ftate it continued feveral 
months, when the tube was broke by an 
accident. The infide of the glafs tube 
above the concreted folution was covered, 
on the inclining fide, with white fpiculcey 
efpecially about the middle, where they 
formed a folid mafs, but confined to a fmail 
fpace. Nearer the bottom of the tube, 
the fpiculae were longer, but fewer in num- 
ber. I imagine that the fpirit of fait had 
difiblved part of the fubftance of the glafs, 
the watery part entering into the faline 
fubftance formed by their union, as in the 


io6 Obfervatlons on 

former experiments, and that there was not 
moifture enough left to keep the folution 
fluid, except when it was warm. 

When I kept a tube containing a quan- 
tity of this faturated folution a day or two 
before a common fire, there was a fmall 
quantity of whitilh matter in the liquor 
itfelf, but very little adhered to any part 
of the tube. 

■" A faturated folution of flowers of zinc 
expofed to the fame degree of heat, in the 
fame manner, for three or four days, was 
tranfparent, but had depofited a brownifh 
itiatter, and there was a flight whitifli 
incrullation about four inches above the 
furface of the liquor. The appearance 
was nearly the fame when the tube was 
examined about four months afterwards, 
when it had been in the fand furnace all 
the time, 

• A faturated folution oilime expofed to the 
heat of a common fire in a glafs tube made 
a large incruilation on the glafs. 

Since common fait contains the marine- 
acid, I faturated a quantity of water with it, 


the Marine Acid, i^cij^ 

and expofed a little of it to the heat of the 
fire, in a long glafs tube hermetically feal- 
ed, making it boil about an hour. When 
it was cold, I perceived that the liquor 
was fenfibly cloudy. I then placed the 
tube in the fand furnace, and examining 
it about a month after, the folution was 
tranfparent, and the glafs had acquired a 
thick white incruftation an inch above the 
furface of the liquor. Four months after- 
wards, the folution was ftjll tranfparent, 
and the white incruftation extended half an 
inch below the furface of the liquor. There 
\!fas alfo a thinner incruftation about two 
inches long, at the diftance of three inches 
above the furface, and likewife fpecks of a 
whitifh matter in feveral parts of the tube 
to the very top of it. Thefe incruftations 
were either formed by the marine acid dif- 
engaged by the folution, or by the watery 
part of it corroding the glafs, or perhaps 
l?y both thefe caufes. 


Xq$ Ohfervatlons on 


'Bxperiments relating to the Difcbarge of the 
Colour of various Solutions made by the 
Marine Acid. 

I HAVE mentioned one inftance in which 
a coloured fpirit of fait had its colour 
difcharged by a fecond faturation. After-^^ 
wards I accidentally found another fubftance 
that produced the fame efFe(5t -, and having 
had the curiofity to carry my obfervations 
relating to this fubjed to fome length, I 
was fortunate enough to fucceed in the in-» 
veftigation beyond what I expedied, though 
much ftill remains to be afcertained with 
reipe£bjto it. 

I had been extracting air fronx cream of 
tartar by means of oil of vitriol, iirft in a 
phial with a ground ftopper, wit}i very lit-* 
tie heat, and then with a red hot fand heat:. 
The black refiduum I diiTolved in fpirit of 
fait, which was of the ufual ftraw colour, and 
I found that inftead of giving any colour to 
it (which confidering the blacknefs of the 
t fubflance 

the Marine Add. tb() 

fubftance, I fully expedted) made it perfecSlly 
colourlefs like water y and, during the folu- 
tion, I perceived a ftrong fmell of liver of ful- 
phur. Afterwards I had the fame refult from 
the refiduum of a mixture of oil of vitriol 
and cream of tartar, which had not been 
calcined. This matter being expofed to the 
open air attraded the moiilure of the at- 
mofphere very ilrongly, and had the con- 
fidence and fmell of treacle. In time the 
more folid part formed itfelf into a cake, 
and pouring off the watery part, I dried the 
reil for other purpofes. 

After this I had the fame effedt from the 
mere coal of cream of tartar, calcined to 
blacknefs. The fmell of this tartar, dur- 
ing the calcination, exacftly refembled that 
of fugar or treacle. To fpirit of fait, this 
coal, which was diiTolved by it very rapid- 
ly, gave no colour whatever -, but, on the 
contrary, difcharged whatever colour it had 
acquired by any other impregnation j pro- 
vided that, as in all the former cafes, the 
colour was not too deep in proportion to 
the quantity of the coal of tartar. For the 


no Obfer^ations on 

purpofe of thefe experiments I happened 
principally to make ufe of a quantity of 
ipirit of fait which had acquired a beautiful 
yellow colour from the folution of the 
white matter that remains after diflilling 
to drynefs a quantity of common oil of 
vitriol, the colour of this folution being 
ealily difcharged by a fmall quantity of the 
coal of tartar, and thereby anfwering my 
purpofe remarkably well in the fubfequent 

Tartar calcined to wliitenefs (the black 
colour being expelled by long continued 
heat) had the fame efFedl on the coloured 
ipirit of fait with the black coal of tartar, 
and was diffolved with equal rapidity. The 
power of this coal of tartar to difcharge 
the colour of fpirit of fait was exhauiled by 
being ufed for this purpofe. For. when 
it had difcharged the colour of one impreg- 
nation, and was taken out, well wafhed, 
and dried, it had no effedl a fecond time. 
It alfo loft this virtue by being wafhed 
with fpirit of fait that had not been colour- 
ed with any impregnation. 


the Marine Add. in 

The folution of fait of tartar in fpirit of 
fait very much refembled the folution of 
the coal of tartar in it, and after the longeil 
calcination that I ever gave the coal of tar- 
tar, it Hill yielded a great quantity of fixed 
air. But, ilotwithflanding this refem- 
blance, the fait of tartar had no efFe<fl on 
the colour of this acid, neither was the 
colour fenfibly affeded by an impregnation 
with fixed air. It was not, therefore, the 
fixed air in the tartaf that had produced 
this efFed;. 

I have obferved that the coal of tartar, 
during its folution in the fpirit of fait, 
emitted a fmell of liver of fulphur. This 
gave me the hint of trying liver of fulphur 
itfelf, and I prefently found it anfwered my 
purpofes much better than the coal of tartar 
itfelf, difcharging inftantly the deepeft 
yellow colour that the acid ever acquired. 
It was evident, therefore, that the difcharge 
of the colour was owing to fomething com- 
mon to the coal of tartar and- liver of ful- 
phur, which I imagined to be phlogiilon in 
fome common fcate, ?.n hypotliefis which 


112 Ohfervations on 

was rendered more probable by an experi- 
ment that will be recited prefentiy ; though 
it is certainly not favoured by the flowers of 
zinc producing the fame effedt. 

The moft remarkable circumftance re-» 
lating to the difcharge of the colour of 
fpirit of fait is that, when it is expofed to 
the open air, it never fails to recover the 
colour that had been difcharged, and a 
very little air confined in the fame phial 
with it is fufficient for the purpofe. 

The firft time that I obferved this, was 
when I had coloured a quantity of fpirit of 
fait with the refiduum of oil of vitriol, 
which, as I have obferved, gives it a yellow 
tinge, and had difcharged the colour by 
the folution of black coal of tartar. For 
when I had, for fome purpofe or other, 
taken out the ftopper of the phial in which 
it was kept, I found that, in a few days, it 
had completely recovered its former yellow 

When this procefs is made in a tall phial, 
it is pleafing to obferve how the reftoration 
of the colour begins at the top, and, in the 


the Marine Acid, 1 1 5 

coUrfe of a few days, defcends gradually to 
the bottom. But let it be kept ever fo long 
in a phial clofe flopped, where no air can 
have accefs to it, aUd it will always con- 
tinue colourlefs. I once kept a quantity of 
fpirit of fait, firll: coloured, and then ren- 
dered transparent, in this manner, feveral 
months, in a phial with a glafs ftopper, and 
it continued colourlefs all the time; but 
upon taking out the ftopper, it recovered in 
a few days its original colour, but more 
coal of tartar difcharged this colour a fecond 

I once had an inflance of a quantity of 
this acid recovering its colour fpontaneoufly 
in a manner that I cannot well account for« 
After the colour had been completely dif^ 
charged> it had been confined in a phial 
with a glafs flopper, and a very fmall 
quantity of air. In thefe circuinflances it 
Recovered its colour in two or three days % 
but, in a few days more, without having 
been opened in the mean time, it was found 
colourlefs again. I fuppofe there might re- 
main enough of the black coal in the acid 
I to 

114 Oifervaftons on 

to difcharge all the colour it had been able 
to recover by means of the air on its fur- 
face j but then why did not the fame 
caufe prevent its recovering its colour at all ? 

Something limilar to this w^as the fol- 
lowing obfervation. On the 19th of No- 
vember 1778, having a quantity of fpirit 
of fait which had acquired a deep yellow 
colour from various impregnations, I took 
two equal quantities of it, and putting them 
into equal phials, I difcharged the colour 
of one of them with liver of fulphur, and 
that of the other with Jlowers of zinc, ob- 
ferving that a large quantity of the latter was 
neceffary for the purpofe, but only a very 
fmall quantity of the former* In the dif- 
charge of the colour with the flowers of 
zinc I alfo perceived a flight fmell of liver 
of fulphur. 

Thefe two phials, containing equally 
colourlefs fpirit of fait, I covered with 
equal jars of common air fl:anding in water; 
and in a day or tv/o perceived that the acid 
in both of them had begun to recover its 
vellow colour j but that in which the 


the Marine Acid xit 

colour had been difcharged with flowers of 
zinc went no farther than about half way 
towards the bottom of the phial, and then 
the acid gradually became colourlefs again j 
whereas the acid in the other phial com^ 
pletely recovered its former colour. Thus 
they continued without any appearance of 
a farther change, till December 3, when 
I examined the air to which they had been 
expofed, and found it nearly in the fame 
ilate in them both, and conliderably 
worfe than common air. With the air 
expofed to the phial with the flowers of 
zinc the meafures of the tefl: were 1.35, 
and with the liver of fulphur, 1.33. With 
the common air, at the fame time, they 
were 1.2. Confidering the difference of the 
circumftances in this experiment, I had 
€xpedled a greater difference in the refult. 

I 2 SEC- 

Ii6 Objervattons on 


Of the Vitriolic Acid. 

TH E mofl remarkable obfervation that 
I have made relating to the vitriolic 
acid v^ill be found under the article of ni- 
trous vapour with v^hich I impregnated it, 
and w^hich precipitates all the vitriolic, acid, 
in the form of cryftals, and leaves the 
water in the polTeffion of the nitrous acid* 
My other obfervations are neither nume- 
rous, nor important. 

It is well known that there is an earthy 
matter in the common oil of vitriol. But 
this I find is not elTential to it : for almofl 
the whole of it is depofited in the firfl diflil- 
lation, and when I diftilled this acid a fe- 
cond time there was little or none of it left. 
On this account, oil of vitriol that is con- 
centrated by merely boiling the water out 
of it is not quite tranfparent, the earthy 
riiatter being difperfed in it, but that which 
has been diflilled twice may be as highly 

, ■ con- 

the Vitriolic Add, i\j 

concentrated as poffible, and yet be as ^ 
tranfparent as water itfelf. 

I tried the efFed: of a long continued heat 
on this as well as on the other acids, but 
was not able to make any fenfible change in 
it. Whatever vapour was raifed from it was 
condenfed again ; though, in time, the glafs 
veiTel in which it was contained was a little 

When a quantity of oil of vitriol is 
thrown into an open lire, it is evaporated 
in denfe white fumes. Thefe I had fuf- 
pedied to be the acid vapour joined to 
the water which it found in the atmo- 
fphere; but I find the fame white denfe 
vapours in the clofeft veiTels, and when the 
acid is in its moft concentrated ilate -, fo 
that it muft be the natural form of the 
vapour in a certain degree of heat. For in 
a greater degree of heat the fame vapours 
are colourlefs. It cannot, however, be faid 
that the acid of vitriol, in a ftate of the 
greateft concentration to which we can 
bring it, is wholly uncombined with 
water. The whitenefs of thefe vapours is 
probably owing to the inequality of den- 
I 3 fity 

il8 Obfervations on 

fity between thera and the air, or vapour of 
other kinds, with which they are mixed 
when it is beginning to condenfe. For 
when they are fo copious as to exclude 
every thing elfe, and the heat is fo great as 
to prevent condenfation, this vapour is as 
pellucid as the glafs itfelf. 

I expofed to the heat of a common fire, in 
a glafs tube about half an inch in diameter, 
and four feet long, as much oil of vitriol as 
filled about two inches of it ; and making it 
boil violently for two hours, obferved no 
change of colour in it. At the firfl boiling 
a quantity of opake vapour iffued out of it, 
and kept dancing there three or four inches 
above the furface of the acid all the time 
it continued to boil; but when the whole 
was cold it was as tranfparent as ever. I 
made it boil about an hour after this, but 
the quantity of white vapour was not fen- 
fibly increafed, as is the cafe with the red 
vapour of the fpirit of nitre. When, after 
this, I foftened the glafs of the tube with 
a blow-pipe, it was preiTed inwards, 
but not fo much as to give me a fufpicion 


the Vitriolic Acid, 119 

that there had been any diminution of the 
air within the tube. 

In the courfe of the diilillation of vi- 
triolic acid thefe white vapours never fail 
to be raifed by heat, to retire to a diflance 
from the acid during the increafe of the 
heat, and to return towards it during its de- 
creafe, exadly like the red vapours with re- 
fped: to the nitrous acid, which is a phe- 
nomenon altogether independent of water. 

When I melted with a blow-pipe a part of 
a hot glafs tube containing vitriolic acid, 
which was quite tranfparent, there rufhed 
out of it, with vaft impetuoiity, a denfe 
cloud of white vapour. Within the tube, 
where the vapour was equally diftributed, 
there was no perceivable opacity; but on 
rufhing out it began to be difperfed, I fup- 
pofe, unequally, as well as to unite with 
the watery vapours which it met with. 

I then tried the efFed: of a flill flroneer 
heat, putting a quantity of the con- 
centrated acid of vitriol into a glafs tube, 
which I placed in a fand furnace, in which 
it continued three or four hours, the fand 
I ^ being 

120 Obfervations on 

being red hot. The next day, when it was 
cold, I found a white incruilation quite 
round the glafs, a little above the fur- 
face of the acid, and likewife another in- 
cruilation about an inch higher up in 
the tube, a little of which was waihed off 
by fhaking the acid. Still the glafs, when 
foftened by heat, was preifed inwards, fo 
that there was no permanent elaftic vapour 

After this I expofed a larger quantity of 
ihs. vitriolic acid to a more moderate fand 
heat, for a greater length of time. But after 
being expofed feveral months in a fand fur- 
nace, there was no feniible change made in 
the acid, nor did any material obfervation 
occur to me. A little whitifli matter, in- 
deed, was pbferved at the bottom of the 
tube, but it feemed to be nothing more 
than the eifed: of the corrofion of the glafs. 
For when it v/as taken oit, the furface of 
the glafs was found to have lofl its polifli. 

^PatTiQ^^ comes that white matter that 
is depoiited in the concentration of oil of 
vitriol I cannot tell, but it is probably fome 


tht Vitriolic Acid, 1 2 1 

earthy matter derived from the fulphur from 
which it is extracted. 

Perhaps fome of the following obferva- 
tions may ferve to throw a little light upon 
it. Having got a fmall quantity of it by 
the concentration of a large quantity of oil 
of vitriol, I poured fpirit of fait upon it, 
and obferved that it was not prefently af- 
feded by it, but in time it was completely 
diffolved, and gave a beautiful yellow tinge 
to that acid, the fubflance itfelf alfo turn- 
ing yellow. In the nitrous acid it v/as not 
aifediedat all, and retained its whitenefs. 
. Having wafhed a quantity of this white 
fediment in diililled water, I evaporated 
that v/ater in an open glafs velTeJ, and ob- 
ferved that, towards the end of the pro- 
cefs, a fmall concretion was formed and left 
upon the glafs, as if this matter had been 
in part dilTolved in the water, and when it 
was nearly ended, a denfe white vapour 
ilTued from it^ which had the fmell of 
treacle or burnt fugar. 

I formerly obferved that a quantity of 
black matter was formed by heating ether 


r22 Obfervations on 

in oil of vitriol, in order to get from it 
vitriolic acid air. This matter was but lit- 
tle afFed:ed by fpirit of fait, but it gave a 
yellov^ tinge to it. The quantity of this 
matter does not feem to depend upon the 
quantity of the ether in the mixture. For 
when I heated equal meafures of ether and 
oil of vitriol, I did not get more of it 
than when I had ufed a much lefs propor- 
tion of the ether. This fubjecft deferves to 
be inveiligated farther. 


Of the volatile Vitriolic Acid, and Vitriolic 
Acid Air* 

THE volatile vitriolic acid, though 
produced from the fixed vitriolic 
acid, is very confiderably different from it, 
efpecially as it may be diflodged from its 
bafis by the vitriolic acid, jufl as other 
weaker acids are diflodged by thofe that are 
thence called the ftronger. But that volatile 
vitriolic acid is capable, however, of being 


the Vitriolic Acid. JZ7 

brought back to the ilate of the common 
vitriolic acid, and becoming the fame thing 
that it originally was, feveral experiments 
fhew. At the time of my laft publication 
I had found that it was capable of diflblving 
iron. and zinc, and of producing inflami- 
mable air, which is the property of oil 
of vitriol : but I |.had a more deciiive proof 
of the fame thing when, to water faturated 
with vitriolic acid air, I had, for another 
purpofe, put feme earth of alum till it was 
faturated. For, after fix months, in which, 
this folution had been expofed in an open 
phial, and one third of it was evaporated, 
I obferved many tranfparent cryftals formed 
at the bottom of the phial, as well as 
an incruilation on the lides of the phial 
above the furface of the liquor. Thefe 
cryftals were all triangular, of a confiderable 
thicknefs, conned:ed with each other, and 
when examined appeared to be a/um, 
which is known to be the faline fubftance 
formed by the fame earth, and the proper 
vitriolic acid. But the following experi- 
ments in which it will appear that real 
5 fulphur 

124 Ohfervations on 

fblphur IS formed by means of the volatile 
vitriolic acid, exhibit a much more remark- 
sible hdi, and is another proof of the mutual 
convertibility of thefe acids into one 
smother^ - • 

Having expofed various liquid fubftances 
to a continued heat in a fand furnace, 
among others I placed in it a glafs tube, 
about an inch in diameter at the bottom, 
tapering to a point at the top, about tv^o 
feet and an half long, clofed hermetically -, 
.when I had put into it about an ounce 
meafure of diftilled water ftrongly impreg- 
nated with vitriolic acid air, with nothing 
more than a random expediation of fome 
change or other taking place in it. This 
was on the 9th of September ijjy, but the 
refult was much more curious than I could 
poflibly have imagined a priori. I ihall 
note the appearances as I obferved them, at 
the feveral intervals in which I examined 
this tube. 

On the 30th of the fame month this im- 
pregnated water, v/hich continued tranf- 
parent to the end of the procefs> had de- 
pcfitedafmall quantity of black powder; 


the Vitriolic Acid. 12 # 

and alfo a bit of matter exadly likey»/- 
fhur about one eighth of an inch in 
diameter lay among it* Small pieces of 
the fame matter floated on the furface of 
the liquor, and ftreaks of the fame coated 
part of the infide of the tube an inch 
above the liquor. From the top of the tube 
to witkin^ about eight inches above the li- 
quor, were beautiful white cryflallizatio^s^ 
like Jpicu/a, difpofed irregularly^ btat gene- 
rally in. tile form of ftars, the glafa being 
perfed:ly tranfparent between them. 

In this ilate the tube continued, the 
cryftallizations increafing, and feypral times 
changing their places^ to the 20th of Ja^ 
nuary following, when an end was put to 
the procefs. Excepting, however, a place 
of a few fquare inches^ near the furface of 
the liquor j all the lower half of the tube 
was quite free from them, but from thence 
to the top it was pretty thick and equally 
covered, exhibiting a moil pleaiing ap- 

In order to obferve the timey and the mari- 
ner of the formation of thefe cryftals, in 

a greater 

I ±6 Obfervatlons trt 

a greater variety of circumftances, I pla^ 
ced in the fand furnace at different times,- 
a flrong glafs tube about nine inches long, 
and a quarter of an inch in diameter, which 
I funk pretty deep in the fand, in order to 
give it a greater degree of heat 3 and alfo 
two tubes about four feet long, one of them 
half an inch, and the other a quarter of aa 
inch in diameter, putting into the fhort 
tube a quantity of the impregnated water 
about an inch in length, and into the long 
tubes two inches and a half. 

The fhort tube had been put into the 
fand on the nth of Auguft, and on th& 
30th of September following the liquor 
was tranfparent, but the top and part of 
the middle of the tube had many white 
flars Jike cryflallizations. 

Of the long tubes the fmaller had begun 
to have cryflallizations, about one third 
from the bottom in about a fortnight, and 
the wider in about a month. When they 
were examined on the 19th of January 
1778, the large tube had more cryflalliza- 
tions than the fmaller, the greatefl quan- 


the Vitriolic Acid. 1^7 

of them about five inches above the 
furface of the liquor, but they were all on 
one fide of the tube, and there were others 
about fix inches above thefe. There were 
alfo very many between the furface of the 
liquor and two inches above it. The 
fmaller tube had no cryftals near the fur- 
face of the liquor, but a good many about 
five inches above it, and the greateft quan- 
tity was about eighteen inches above '\U 
Neither of thefe tubes had any cryftals in 
two thirds of the upper part of them. . 

Applying the flame of a candle with a 
blow-pipe to the fmaller of the long tubes 
above-mentioned, the glafs was prelfed vio- 
lently inwards j fo that it was evident 
there was a decreafe of elaftic matter within 
the tube, which therefore probably entered 
into the cryilals. If any part of the 
liquid touched the hot glafs, a denfe white 
fume was excited, exadly like that from 
the oil of vitriol. Taking off one half of 
the tube, and then opening it under water, 
it was half filled with water, and the air 
within in it was completely phlogifticated, 


1^8 Obfervafions on 

which agrees with, my former obfervations^ . 
of the vitriolic acid air imparting phlo- 
gifton to common air. 

When I heated the dry cryflals, the fam6 
white cloud was raifed, and the cryftals 
were by this means difperfed into a kind 
of dufl, that incruils the glafs. For I 
applied the heat on the outiide of the tube. 

The liquor itfelf was ilill extremqly acid, 
and the fmell of it very pu^ngent ; fo that, 
probably, only a fmall part of the vitriolic 
acid air with which it was impregnated 
had entered into thefe cryftals, numerous 
as they were* 

The cryftals were eaiily fliaken off from 
the fide of the tube, when it was wafhed 
with the liquor, and they continued undif- 
folved in it. 

The preceding obfervations were made 
prefently after the tubes in which the cryf- 
tals were formed were taken from the fand 
furnace i and in this ftate they continued 
near a year, in the courfe of which I had 
Ihewed them to feveral of my chemical 
friends, v/lio expreffed much furprife at 
4 the 

The Nitrous Acid, 129 

the fight of them. At length I opened the 
tube that contained the greateft quantity of 
thefe cryflals, firil obferving that, when I 
foftened the glafs, it was ftill prefled inwards. 

The cryftals, I found, were not diflblved 
in fpirit of fait, and when they had been 
wafhed, and dried, they had the colour, 
and fmell oi fulphtir ; and being laid on a 
hot iron burned with a blue flame, fo as to 
leave no doubt of the identity of the fub- 

To form this fulphur, I conjedure, that 
the phlogifton which had rendered the 
acid volatile, in this expanded and confined 
flate, had been compelled to form that very 
different and peculiar union requifiteto make 
fulphur. The fad is certainly a remark- 
able one. 

Having obferved thefe curious effed:s of 
the impregnation of water with vitriolic 
acid air, I expofed to the fame heat, in 
fmiilar circumllances, fpirit of wine, and 
oil of turpentine, faturated with the fame 
kind of air. 

K The 

i^o Ohfervations oft 

The impregnated fpirit of wine, after 
being expofed to this heat about a fortnight 
was tranfparent, but had many flender cryf- 
tals in it, and the greater part of the tube 
liad a thick and whitilli incruftation, be- 
ginning about three inches above the furface 
of the liquor, and extending about twelve 
inches, but was thickeft in the middle. 

A fliort tube, containing a quantity of 
the fame impregnated fpirit of wine, had 
no incruftation, but many more cryftals, iil 
the form of fpiculae which fettled to the 
bottom of the liquor. Another tube of the 
fame length had limilar fpiculse, and near 
the top a confiderable incruftation not 

The oil of turpentine impregnated with 
vitriolic acid air, and expofed to the heat 
in this manner, from being of a light am- 
ber colour, became of a deep brown. The 
tube in which it was contained was only 
eighteen inches long, and the upper half 
of it was covered on one fide with white 
incruftations not fpiculine. 


the Nitrous Acid. 131 

Whale oil impregnated with this air, 
from being brown, had probably become 
almoft black. For the tube was broke, 
but had a very black incruftation towards 
the bottom, efpecially near the furface of 
the liquor* 

I alfo expofed to the fame heat tubes 
containing vitriolic acid air only, having 
iirit filled them with quickfilver, then with 
this kind of air^ and afterwards fealing 
them hermetically with a blow-pipe -, and 
the refult was fimilar to thofe in which the 
impregnations were concerned. 

One tube of this kind that had been 
buried in the hot fand on the 1 1 th of 
Augufl, being examined on the 30 th of 
September, was found in the following 
ftate. The upper part of the tube was half 
covered with white cryftals^ but much 
fmaller than thofe in the tubes containing 
the water impregnated with this air. 

Another tube containing the fame kind 

of air, which had been buried in the fand 

a longer time, was found quite covered 

with white cryfbals, and a fmall part of 

K 2 the 

132 Obfervatlons on 

the VOiQ^ was black, probably from fomcp» 
external Accidental caufe. The end of thi& 
tube being broke under quicklilver, it filled 
one third of it, and water abforbed all that 
remained of the air, except a very fmall 
bubble. This water had the fmell of water 
impregnated with vitriolic acid air. 

It is evident that this acid air had been 
in part thrown into the form of folid cryf- 
tals by this expofure to heat ; but then with 
what fubftance was it united, or did the 
air contain within itfelf the principle of 
this combination, but wanted the a(3;ion of 
fuch an external force to bring them. ijit<^ 
this kind of union ? 

I have feveral times repeated this expe-: 
riment, and have never failed to find the 
iniide of the tubes that had been filled with 
vitriolic acid air coated with this white 
matter; but it is fo exceedingly flight, that 
I cannot make many obfervations upon it. 
I am rather furprized to find that it does 
not feem to be fulphiiry which is formed 
from the heating of water impregnated 
with the fame kind of air. For fpirit of 


the Phofphoi-ic Acid, # 1^3 
feJt feems to diffolve it all. At lead the 
tvibe is wafhed perfectly clean with it, and 
I could not difcern any thing in that acid 
afterwards. But this may be owing to the 
very fmall quantity of it, though it be 
fpread on fo great a furface, and to the ex^ 
treme minutenefs of the particles of which 
it cOniifls. 

S E C T I O N XV. 

Of the Phofphoric Acid. 

AVING made fo many experiments 
on the acids, with a view to reducing 
them to the form of air, and upon their 
properties when exhibited in that new 
form, it might have been expeded that I 
fliould, before this time, have taken notice 
of the phofphoric acid, which is fo remark- 
ably different from the other acids, and 
which bears fo near a relation to the animal 
©economy. The true reafon of this feem- 
ing negled of fo important a fubje<5t of 
.experiment was the expence neceffary to 
K 3 procure 

134 11 Obfervafions on 
procure it in any tolerable quantity. At 
length, however, I procured a quantity 
fufficient for a few experiments, not un- 
deferving of being related. 

Chemifts do not need to be informed of 
the method of procuring this liquid acid 
from folid phofphorus -, but for the fake of 
perfons of only a general philofophical 
turn, like myfelf,. it may be worth while 
to obferve, that this acid is eafily procured, 
with time, by expoling it to the open air 
in the mouth of a funnfel, going into a 
phial which receives the acid, as the phof- 
phorus gradually waftes by this kind of 
accenfion. It muft be fet in a place neither 
very cold, nor very warm. But this depends 
upon the conliftence of the phofphorus, and. 
other circumftances, which muft be learned 
by experience. If it fmokes very much, 
it is a lign that it is too warm, atid is in 
danger of taking fire, in which cafe it may 
be faved by plunging it inftantly in water. 

Having procured my phofphorus, I firft 
obferved, that the water in which it had 
been long kept had nothing acid in it. 

the Phofphoric Acid, 135 

For, being mixed with water made blue 
with the juice of turnfole, it did hot afFed: 
its colour, which ihews that no proper de- 
compofition of it takes place in water. 
Having then expofed it to the open air, in 
the manner defcribed above, I got a quan- 
tity of the acid with which I made the 
following obfervations. 

With refped to air-y this acid very mwch 
refembles radical vinegar, or rather the vitri- 
olic acid. For though the application of heat 
converts it into vapour, it is all condenfed 
again in the temperature of the atmofphere, 
and no part of it remains permanent elaftic 
air. I made the experiment in a glafs tube 
bent a little like a retort, the open end of 
which turned up into a vellel filled with 
quickfilver, and immerfed in a bafon of 
the fame. When I made the acid boil, the 
vapour paiTed into the recipient, but it was 
wholly condenfed there, and the liquor fo 
colleded did not differ, as far as I could 
perceive, from what it had been before the 

As, like the vitriolic acid, this gave no air 
K 4 , ^f 

136 Obfernjations on 

of itfelf, I thought that, like this ac^d, it 
might poffibly give fomething iimilar to 
the vitriolic acid air by means of fubftances 
containing phlogifton. With this vievy \ 
kept it in a boiling heat both v^ith quick- 
filver, and alfo with fpirit of wine, but 
without any effed:; and even the com- 
mon air, that was expelled from the phial 
in which the experiment was made, was 
not feniibly phlogifticated. 

This acid, however, refembled that of 
vitriol and radical vinegar in this, that it 
readily dilTolved iron, efpecially with the 
aid of a little heat, and with it yielded ^ 
ilrong inflammable air. But there is fomer 
thing more remarkable in the produce of 
inflammable air from it by means of 

In order to try whether this acid had 
any of the properties of the nitrous, I mix^ 
cd it with fome minium out of which all 
the air had been expelled by heat. This 
fubftance, in this flate, I had found, when 
mixed with nitrous acid, yields dephlogif- 
ticated air, but no air at all with the vitri- 

the Phofp baric Acid. ' f 35? 

olic or the marine acid. The phofphoric 
^cid mixed with this minium with little 
pr no fenfible heat, but the mixture expofed 
to the flame of a candle yielded air very 
plentifully, and it was very turbid'. I 
received it in lime water, but it did not 
precipitate the lime, except in the fmalleft 
degree. The air I got in this method was 
not aiFed;ed by nitrous air, nor did it affed: 
common air, but was ftrongly inflammable, 
burning with a bright white flame i and 
the fmell of the ak was the fame v^ith that 
of the fl:rong fmell of phofphorus. The 
yellow minium became of a darkifh grey 
colour, or nearly black by this procefs. 

Having a quantity of the mixture of 
phofphoric acid and fpirit of wine, remain- 
ing, from the experiment above-mentioned, 
and not being willing to lofe it, I likewife 
mixed it v/ith fome of the fame minium, 
and I had the fame refult. The common 
' air that was fir ft Expelled from the furface 
of the veflel in which the experiment v/as 
made was not much injured, the next that 
came had a fmall quantity of fixed air in 


138 Obfervations on 

it 5 but all the remainder was ftrongly in- 
flammable, burning with a yellow flame, 
the next was more weakly inflammable, 
and the laft produce was phlogifl:icated air 

It fhould feem that the ^arth of the 
minium enters into the compofition of 
this inflammable air, fince the acid itfelf 
could not fupply it, and the air was ex- 
ceedingly turbid when it was firfl: pro- 
duced. But I fhould think that the phlo- 
gifton muft have been fupplied from the 
acid, fince the minium, I believe, does not 
contain it. 

About the time that I was making thefe 
experiments I was making obfervations on 
the expofure of a variety of fluid fubfl:ances 
to a long continued heat. I therefore 
treated this acid in the fame manner, firfl 
in a long glafs tube, held in an inclined or 
nearly perpendicular pofition, and then in 
a horizontal one, expelling the acid by the 
heat from one part of the tube to the other ; 
the refult of which procefs was remarkably 
different from that of the other. 


the Phofphork Acid* 139 

In a glafs tube about thirty inches, in 
length, and one third of an -inch in diame- 
ter, I put as much of this acid as filled 
about an inch of the tube in length, and 
making it boil, there was a white vapour 
at the height of about fifteen or eighteen 
inches above the furface of the acid, con- 
tinually dancing up and down as it boiled. 
At and below this part of the tube, it was 
very hot, but immediately above it was 
quite cold. I kept the acid boiling feveral 
hours without any fenfible change. 

Though the phofphoric acid was not 
changed by boiling feveral hours in the courfe 
of two days, in a glafs tube hermetically feal- 
cd, and placed in nearly a vertical pofition, 
yet when I applied the flame of a candle 
to any part of the tube, after the acid had 
left it moifl (when it had been made to 
flow to the other end) the glafs was infl:ant- 
\y covered with a white incrufl:ation 3 and 
repeating this procefs, at each end of the 
tube alternately, I quickly made the whole 
folid. At leafl: there was no more moifl:ure 
in xhQ tube th|n adhered to the fides of it, 


tj^o O^Jervatlons on 

and could not be made to flow at all. This 
experiment I repeated in feveral tubes, and 
always with the fame event, whatever was 
the quantity of the acid. 

When the tube was made very hot there 
would fometimes be flashes of light in the 
infide, extending the whole length of the 
tube ; and of thefe there were fometimes 
three in the fame tube at different times* 
Whenever this happened, a part of the 
tube always acquired a thin coating of 
orange coloured matter, fuch as remains 
upon glafs v^hen phofphorus is really 
ignited upon it in the open air. 

The white matter thus left in the glafs 
tubes attracted no moifture from the atmo- 
sphere, at leafl no fenfible quantity of it, 
and it was not at all affeded by fpirit of 
fait. It did not even long retain any £cn* 
iible acidity 5 for when it had been wafhed 
ieveral times, the water in vvrhich it lay 
-(Aid not even turn the juice of turnfole red. 

If I be afked what I think becomes of 
the moifture which rendered the phofphoric 
acid liquid in this procefs, I ihould fay 


Mercury. t^x 

that, as in the fimilar experiments with the 
marine acid, it difTolves the glafs, and with 
it the acid and water both unite in a folid 
form, as in other cryftalizations ; and 
iince I made thefe experiments> I have 
been informed by Dr. Ingenhoufz, a man 
©f a truly philofophical and experimental 
turn, that the phofphoric acid, when 
hot, diiTolves glafs, exactly like the fluor 


Obfervations relating to the black Powder 
produced by the Agitation of impure ^ick- 

lOERHAAVE found that quickfilver, 
by very long continued agitation, was 
iri part converted into a black powder, 
which is often feen on the furface of it, 
and which, I believe, is generally deemed 
to be a partial calx of this metal, the mer- 
cury having parted v/ith fome portion of 
its phlogiflon in this procef&. It is thought, 


142 Otffertattons on 

however, that it is no great proportion oi 
its phlogiflon that it parts with in ordef 
to afTume this new form of black powder, 
becaufe it is not poffible to expofe it to any 
confiderable degree of heat without com- 
pletely revivifying the whole of it. Even 
mere trituration has been obferved to have 
the fame effedt. On this account, fome 
do not confider this procefs as a proper cal-* 
eination, but fuppofe the mercury only to 
have alTumed a new form, really containing 
all the phlogifton U. was ever poffefTed of* 
And it will be in my power to fhew, in 
the courfe of this work, that there are 
feveral cafes in which mere heat produces 
the fame eifedt, to appearance, with the 
addition of phlogifton. 

Notwithftanding this, 1 think it will 
appear from the refult of my obfervations 
on the fubjed:, that this black powder is 
really mercury fuperpblogifticafed, having 
acquired more phlogifton, infliead of having 
parted with any that had properly belong- 
ed to it; that various fubflances agitated 
together with mercury give it this over- 

Mercury, 14^ 

charge of phlogifton, and to appearance 
refume it again. I alfo hope to fhew in 
one view all the fteps in the complete pro- 
grefs of mercury from this fuper-phlogif- 
ticated flate to its proper dephlogifticated 
ftate, the precipitate per fe, in which it 
aflumes four very different appearances. 
For the greater fatisfadion of my readers, 
I fhall, as I generally have done, relate my 
obfervations hiftorically. 

Having been under a neceflity of making 

much ufe of quickfilver in my experiments 

relating to air, in order to feparate and 

prefervc thofe kinds that would have been 

abforbed by water, and being frequently 

obliged to remove my apparatus from the 

country to London, and from London to 

the country, I could not help being ftruck 

with a quantity of black powder, which I 

fometimes found upon the furface of my 

quickfilver -, when, at other times, and, 

as far as I could judge, in the fame circum- 

ftances, I found very little, or none at all. 

It was evident, however, that whatever was 

the catife of this appearance, the agitation 

2 of 

744- Obfervatlons on 

of the carriage had contributed to it ; for^ 
except in thofe circumiliances, I ilevei^ found 
any of it. At one time I found, after re- 
moving my quicklilver, which was about 
twelve pounds, from London into the 
country, there was near a pound of this 
black powder on the furface of it. This 5 
thought a great acquifition, as it Wa$ a 
quantity fufficient for a variety of exrperi- 

The firfl; thing that occurred to me to 
do with it was to endeavour to expel air 
from it by means of heat. Accordingly, I 
put a quantity of it into a glafs phial with 
a ground flopper and tube, and, with the 
heat of a candle, I prefently expelled from? 
it a quantity of air ; which being admitted 
to lime water made it very turbid, and was, 
in a great meafure, abforbed -, a proof that 
the air it had contained was in part fixed 
air, and the remainder was not fo much 
diminifhed by nitrous air as common air 
would have been j fo that no pure air came 
from this black powder, and confequently 
it differed effentially from the precipitate 


Mercury. i^^ 

fer fe, which would have yielded no 
iixed air, but the pureft dephlogiflicated 
air oi)ly. I obferved alfo, at the fame 
time, that the powder at the bottom 
of the phial, which had been expofed to 
the greateft degree of heat, had become 
yellow. This was evidently fomething 
elfe than could have come from the quick- 
iilver, but I did not at that time difcover 
what it was. A good deal of the quick- 
filver was revivified by the procefs. 

Expofing another part of this black 
powder to a red fand heat in a glafs velTel, 
I produced a greater quantity of fixed air. 
Alfo, part of the black powder became 
yellow, as before; and triturating the 
Avhole of it in the palm of my hand, it 
aflumed a kind of dirty green colour, and 
about one half of it was pretty readily 
converted into quickfilver. Putting the 
remainder of this greenifh powder into a 
thin glafs vefiel, and holding it over the 
flame of a candle, about one half of it 
became. a perfedly yellow powder, and the 
jreit was evaporated, and being in part 
L colleded. 

t46 Obfervations on 

colleded, appeared to be pure quick- 


By this means I efFed:ed a complete 
reparation of the quickfilver which had 
conflituted the blacknefs of the powder, 
and had a perfedly diftind: yellow fubflance 
behind, the nature of which an experienced 
chemift would have immediately diftin- 
guilhed ; and I difcovered it foon after- 
wards. I prefently concluded that, not- 
withftanding this yellow fubftance feem- 
ed to be produced from the quickfilver, 
and had great fpecific gravity, it was not 
of the nature of precipitate per fe, becaufc 
it had yielded fixed air. With another 
part of the black powder I found that the 
fixed air it yielded was feveral times the 
bulk of the powder, but I did not afcer- 
tain with exad:nefs what the proportion 

Being ilill ignorant of the conftitution 
of this black powder, and l>eing, confe- 
quently, unable with certainty to procure 
a quantity of it, I confidered what other 
fubftances into which mercury entered had 
the fame appearance, and among others I 


Mercury, 147 

fufped:ed that JEthiops Mineral, which is 
a compofition of mercury and fulphur, 
rnight perhaps be the fame thing, and if 
fo, it might be eafily procured in any quan- 
tity for the purpofe of future experiments. 
But I prefently found that this fubftance, 
treated in the fame manner in which I had 
treated my black mercurial powder, yield- 
ed no air all. 

Difappointed in this exped:ation, and 
being very delirous of procuring a quan- 
tity of this black powder, I took feveral 
quantities of this quickfilver, in the fime 
ilate in which I had generally ufed it, and 
therefore, as I hoped, in the fame ilate in 
which it had yielded the black powder be- 
fore; and in order to treat it as nearly as 
poffible in the fame manner, I put it into 
fuch earthen pots as I had before made ufe 
of in conveying it from one place to ano- 
ther; and farther to promote a more mi- 
nute divifion of its parts, I fometimes put 
fand, and other fubftances on which I knew 
it could have no chemical adion, into the 
pot along with it. I then put thefe pots 
L 2 into 

14S Obfervations on 

into fmall boxes, and procured them to Be 
faftened to poft chaifes, and other car- 
riages, and had them brought to me ag^in 
after they had undergone, at leafl, as muclj 
agitation as the former quicklilver had 
done in lis paflage from London to Wilt- 
fhire. But this produced no feniible ef- 
fe<5l ; the quickfilver, as it appeared after- 
wards, being then too pure for that pur- 

At length it occurred to me that the 
quickfilver having been ufed for a great va- 
riety of purpofes, and confequently haying 
been expofed to a great variety of impreg- 
nations, it might have got fome metallic 
ones, and particularly from lead or tin. I 
therefore diiTolved a fmall quantity of lead 
in fome mercury, and prefently found that 
a very flight agitation covered it vvith 
black pov^der, and obfcured all the inlide 
of the velTel. 

Being now in pofTeiTion of what had been 
fo long the objedt of my willies, and being 
able to procure this black powder at plea- 


Mercury. 149 

fure, I was prefently led by it to other ob- 
fervations both curious and ufeful. 

In order to obferve the nature and pro- 
grefs of this operation to more advantage, 
I filled a glafs phial, of about ten ounces, 
one fourth part full of this mixture of 
mercury and lead; and inverting it in a 
bafon of the fame, I agitated it vi^ith my 
hand, and prefently found that the air 
within the phial was fenlibly diminiilied, 
an evident proof that it was phlogiflicated i 
and in about ten minutes the diminution 
amounted to one fifth of the whole, after 
which no agitation had any more effed: 
upon it. Examining this air, I found, as 
I expedled, that it extinguiflied a candle. 
Indeed it was completely phlogiflicated; 
i^pt being at all affedted by nitrous air. 

I was now fully fatisfied that this 
was what I have called a proper phlogijlic 
procefs with refped: to air, fimilar to the 
calcination of metals by heat i the air 
being affedled in the fame manner, and that 
when mercury and lead were thus re- 
duced to an amalgam, the fimple expofurc 
L 3 to 

150 Obfervations on 

to air wa& fufficient to produce the calcina- 
tion of one of them at leaft; and, as I then 
thought, of both, agreeably to the common 
opinion concerning the nature of the black 
pov/der of mercury. 

I was abundantly confirmed inmyfuppo- 
fition, by finding that when, inftead of 
common air, I agitated this amalgam in 
fixed air, nitrous air, inflammable air, or in 
any kind of phlogifticated air, no black 
powder was produced, and thofe kinds of 
air remained unaltered. When, indeed, I 
agitated this amalgam in nitrous air, the 
furface of it prefently aifumed a blackiih 
hue, but this foon nearly difappeared, and 
no farther agitation produced any fen- 
fible eifed:. But when, on the contrary, I 
made this agitation in dephlogifticated air, 
the black powder was generated ex- 
ceedingly faft, and the air went on di- 
minifhing, till what remained was one 
fourth lefs than the whole. 

It now occurred to me that, by means of 
this ' agitation, I might expell the whole 
of any quantity of lead, or other metals, 


Mercury. i£i 

from the mercury with which they might 
be mixed ; and I foon found it to be an 
eafy and excellent method, not at all infe- 
rior to diftillation. As I have repeated 
this procefs many times, and always have 
recourfe to it when my mercury has ac- 
quired any metallic mixture, I fh-^ll de- 
fcribe the manner in which I find it is moft 
expeditioufly done ; though a novice in the 
procefs muft not exped: to fucceed per- 
fectly well at the firft trial. 

I take a glafs phial with a ground ftopper 
(fuch being generally pretty flrong) con- 
taining ten or twelve ounces of water, and 
£11 about one fourth of it with the foul 
quickiilver; then, putting in the ftopper, 
I hold it inverted with both my hands, and 
fhake it violently, generally ftriking the 
hand that fupports it againil my thigh. 
When I have given it twenty or thirty 
flrokes in this manner, I take out the ftop- 
per, and blow into the phial with a pair 
of bellows, which I do in order to change 
the air that has become in part phlogifti- 

L 4 cated, 

1^2 Obfertjations on 

cated, and knowing that the purer the air 
is the fafter the procefs advances. 

After a fhort time, if the mercury be 
very foul, the furface will not only he^ 
corn6 black, but a great quantity of the 
upper part of it will be, as it were, 
coagulated, fo as to be eafily feparated froril 
the reft. I therefore invert the phial, arid 
covering the niouth of it with my finger, 
let out all the mercury that will flow 
eafily, and put the black coagulated part 
into a cup by itfelf. This I prefs repeat- 
edly with the end of my finger, till I make 
a complete feparation of the running mer- 
cury from the black powder; and putting 
the powder by itfelf, I pour back the rner- 
cury to the reft of the mafs out of whicH 
it was taken, in order to be agitated with 
it again. 

This procefs I repeat till I find that no 
more black matter can be feparated ; and it 
is not a little remarkable, that the operator 
will be at no lofs to know when the procefs 
is completed. For the fame quantity of 


Mercury » i^o 

lead feeitis to come out of it in equal times 
of agitation, and confequently the whole 
becomes pure at once. Alfo, whereas, 
while the lead was in the mercury, it felt, 
as I may fay, like foft clay, the moment 
the lead is feparated from it, it begins to 
rattle as it is fhaken, fo that any perfon in 
the room may perceive when it has been 
agitated enough. * 

That the mercury is made quite pure by 
fliis procefs I afeertained by diilillation. 
For having diftilled in a glafs vefTel a large 
quantity of quickfilver, in which both lead 
and tin had been purpofely diflblved, and 
which had only been agitated in this man- 
ner afterwards, I found nothing more than 
a light whitifh flain on the bottom of the 


* Pure mercury may alfo be diftinguifhed from that 
which is very impure by this circumftance, viz, that a 
mixture of lead or tin, at leaft, very much diminifhes its 
attraction of cohefion. For, v^^hen pure mercury is con- 
tained in a glafs or earthen veflel, there will be a hollow 
fpace between the metal and the veflel ; vv^hereas if there 
be lead or tin in it, the whole furface, even to the place of 
contaft with the veflel^ will be perfedly level. 


154 Obferiiations on 

When a quantity of the black powder is 
procured, it is very eafy, by diftillation, to 
feparate the mercury from the calx, and \ 
^o not know a readier method of procuring 
the calx of lead, or tin, and perhaps the 
calx of other metals alfo. The quantity 
of black mercurial powder is very confider- 
able in proportion to the lead or tin mixed 
with it ; though it is not eafy to afcertain 
this with exadlnefs, becaufe, in en- 
deavouring to feparate the powder from 
the running mercury a good deal of it is, 
by mere trituration, converted into run- 
ning mercury ; and I do not know but 
that, in time, the whole might be re- 
flored by this means, and the calx of 
lead, &c. be got quite pure. However, 
from the following experiments it will be 
^en what proportion they generally bear 
to each other, after a tolerably careful fepa- 
ration. It will be feen alfo, that when all 
the quickfilver that was converted into 
black powder is expelled from lead or tin by 
heat, there will remain more weight of 
the calx than there was of the metal ; as 


Mercury. i^^ 

might be expe(5led. But as I applied more 
heat than was neceffary to feparate the 
quicklilver, a good deal of the air, and 
whatever elfe contributes to the additional 
weight of the calx, is, no doubt, expelled 
with it. 

Having mixed i dwt. of lead with 
about five pounds of quickfilver, I expelled 
it all by agitation, in the method defcribed 
above j when, weighing the black powder, 
it was found to be i oz. lo dw. 5 gr. fome 
particles of the running mercury being, 
however, ftill vifible in it. When the 
quickfilver was expelled by heat, the calx 
of the lead appeared in the form of a 
browniih powder, and weighed i dw. 5 gr. 
Having mixed 1 dwt. of tin with the 
above-mentioned quantity of quickfilver^ 
and having expelled it again by agitation, 
the bbck powder, with fome fmall 
globules of quickfilver mixed with it, 
weighed 2 oz. i dw. 5 gr. and the calx, 
which was a tolerably white powder, 
weighed i dw. 7 gr. 


i^6 Obfervations on 

The reparation of tin from quickfilvei' 
by agitation is not efFe<5led near fo foon as 
ie^d. It requires at leaft four times the 
iabotif. It alfo requires pfoportionably 
more time to feparate the black powder 
from the thick amalgam, in the manner 
defcribed above, 

Quicklilver is feparated from lead or tin 
when the mafs is agitated in water y as well 
as in air, but it feems to require more time. 
In this procefs it is alfo ealily perceived 
when all the bale metal is expelled ; the 
phenomena of the agitation of this amal- 
gatsi atnd of pure mercury in water beiri^ 
very remarkably different. It is even eafy 
to perceive, by this means, in a moment, 
whether the quickfilver be pure or not. 
For if it be impure, the water beeomcs 
dpake the nidment the agitation corii- 
inences, which is by flo means the cafe 
with' pure quickfilver, efpecially if the 
tvater in which it is agitated has not been 
iifed for this purpbfe before, Alfo, the 
black matter fufpended in the water in 


Mercury. i^j 

which pure quickfilver has been agitated is 
(except in a cafe that will be defcribed 
hereafter) prefently deposited -, wherea^s the 
water in which the amalgam has been agi- 
tated does not become clear in feveral days. 
It may alfo be perceived how the quick- 
lilver approaches towards purity, by this 
depofit being made more or lefs readily. 

Alfo, the phenomena during the agita- 
tion in thefe two cafes are ftrikingly dif- 
ferent, though not eafily defcribed in 
Words. More efpecially, the mixture of 
quickfilver with lead or tin does not feem 
to admit the water to mix with it, whereas 
pure quickfilver, by violent agitation, may 
be fo thoroughly mixed with the water, 
that it will fometimes be feveral feconds 
after the agitation is difcontinued, before 
it have entirely difengaged itfelf from th& 
water ; and in doing this it exhibits a very 
pleafing fpedtacle. By this means, as in 
the procefs without v/ater, it may be per- 
ceived at once when the feparation of the 
bafe metal, and the mercury is completely 


1^8 Ohfervations on 

Having a large quantity of water made 
very black with the agitation of a mixture 
of quickfilver and lead, I agitated a quan- 
tity of common air in it a long time, and 
let it Hand feveral days; but the air was 
not fenfibly injured by this means; fo that 
though this water and the calcined amalgam 
fufpended in it do contain phlogiilon, it is 
not by this means imparted to the air. 

I evaporated a pint of the diftilled water 
in which quickfilver and tin had been agi- 
tated, and which had flood till it was 
quite tranfparent, when a white fediment 
remained, but it did not weigh more than 
a few grains. 


Mercury. 159 


Of the Agitation of pure mercury in watsr. 

AGITATION in pure water will con- 
vert the pureft quickfilver into black 
powder, and much more fpeedily than it 
can be effe(5ted in air -, but when this is 
produced in water, this flate of the quick- 
filver is not permanent. But it will give 
my reader more fatisfa(5lion, if I defcribe 
the phenomena of this procefs juft as they 
occurred to me. 

I agitated a pound of pure quickfilver a 
few minutes in diflilled water, when I ob- 
ferved that the water had become opake, 
with particles of a black matter, fo as to be 
impervious to the light. This procefs I 
Repeated feveral hours, changing the water 
as it became black. 

When any quantity of water had been 
once ufed for this purpofe, the fame effed: 
was produced much fooner than it was 
with frelh water ; fo that, though the 

i6.o Obfervations on 

frefh water and this could not be diftin- 
guiihed by the eye, it was prefently per- 
ceived which water had been ufed before. 

After I had continued this procefs, which 
was in a ten ounce phial, with a ground 
glafs ftopper, about four or five hours, 
though with fome interruption, I found 
that the quickfilver had loll 2 dvv^ts. of its 
weight. But, agitating it again little more 
than an hour, with the fame water that I 
had ufed before, I found it had loft in 
all 5 dwts. 

This procefs went on the bell when I 
ufed three or four times the bulk of water 
with the quickfilver. 

That the air contained in the phial toge- 
ther with the water had nothing to do in 
this bufinefs was evident, becaufe the very 
fame effedl was produced when the phial 
was filled up with water only, fo as to ex- 
clude all the air , and this is the man- 
ner in whicli I generally make this experi- 

This black matter diffufed through the 
water becomes white running mercury 


Mercury, i6t 

wh^n it is expofed to the open air only. 
No trituration, or operation of any kind, is 
requilite for this purpofe. 

The water in which this pure quick- 
iilver had been agitated acquired a peculiar 
fmell and tafte, not eafy to be defcribed. 
When a pint of it was evaporated to dry- 
ncfs, there remained a fmall quantity of 
piatter, an account of which will be given 
hereafter. Common air agitated in this 
water was not fenfibly diminifhed, and 
therefore I conclude not fenfibly injured 
by it. 

Spirit of wine feems to anfwer this pur- 
pofe as well as water, but not oil of tur- 
pentine. I expofed them, together with 
various other things, to continued agitation 
in a mill^ for feveral months ; but when 
the phial containing them was examined, 
neither the quicklilver, nor the oil of tur- 
pentine, was fenfibly changed. Of thefe 
obfervations I fhall give a feparate account, 
at the clofe of this article. 

Hitherto I was intirely ignorant of the 

real nature of the black powder into which 

M mercurj 

162 Obfervaftons on 

mercury is converted by agitation in water, 
and rather took it for granted that it was 
a partial calcination of that metal ; though 
I might have recolledled, that no fuch thing 
as this black powder occurs in any part af 
the procefs of a proper calcination of mer- 
cury, in converting it into precipitate per fe. 
Nor did I at length difcover the real na- 
ture of it by any reafoning or conjecSture et 
priori. But having conftantly obferved (what 
-it was impoffible not to obferve) that when-= 
ever I fpilled any of the water containing 
the black powder, the moment it was dry 
it appeared in the form of white running 
mercury, alfo that the glafs funnel I made 
ufe of, in pouring this black water inta the 
phial, was always found white, with fmall 
globules of running mercury, whenever I 
took it up, after an interruption in my ex- 
periments ', I could not but conclude that 
this converfion of black into white mer- 
cury 'was eifecfled by th.Q air, and therefore 
I determined to have- this procefs performed 
in confined air, in order to judge how the. 
air itfelf was afecSted by it. 


MercUrp -163 

Accordingly, having a coniiderable quan- 
tity of this black powder in a little water, 
enough to prevent its becoming running 
mercury, I poured fome of it into ,2. fmall 
retort, and evaporating all the water that 
Was mixed w^ith it, while the neck of the 
l-etort was plunged in water, and admitting 
as little air a^ poffible (barely enough to 
i^revent the retort from breaking by the 
rufhing in of frefh water, -after the bulk 
of the air had been e:5^pelled by the heat 
and vapour within the retort) I examined 
the inclofed air when the VCiTel was cold 1 
and found it to be v^orfe than common 
air. For one meafure of this and one q£ 
-nitrous air occupied the fpace of 1.31 mea- 
fures I when one meafure of the common 
external air and another of the fame nitrous 
air occupied the fpace of 1.27 meafures. 

It was evident, however, that, in this 
experiment^ the air could only be very 
partially affeded by the change of the 
mercury ; fince a great deal muft neceffarily 
have been admitted after all the heat had 
been applied -, and the newly admitted air 
Ms ' mufl^ 

164 Obfer'Vattons en 

muH, of courfe, have diluted that which 
had been afted:ed by the procefs. I there- 
fore made the following more decilive 
experiment, which perfectly agreed with, 
and confirmed, the preceding. 

I took a glafs tube, about eighteen 
inches long, and half an inch wide, and 
pouring • into it a quantity of the water 
and black powder of mercury, turned it 
every way till it had got a black coating 
in all places. I then inverted it, and 
placed it in a cup of water near the fire, 
but not fo near as to convert the water 
within the tube into fteam, and thereby 
expel too much of the air. In this fitua- 
tion I perceived, after fome time, that the 
quickfilver was revivified, all the tube to 
which the heat had reached having now got 
a white coating, and having the appearance 
of a looking-glafs. I then examined the 
air in the infide of the tube, and found it 
to be very fufficiently phlogillicated. For 
one meafure of it and one of nitrous air 
occupied the fpace of 1.66 meafures, not- 
withftanding a confiderable part of the tube 


Mercury. 165. 

li^d not been fo much heated as to have all 
the mercury on it revivified, I repeated this 
experiment in another tube, and with the 
fame refult, the air contained in it being 
as much phlogifticated as before. At 
this tirne the tube being expofed to too 
great a degree of heat part of the mercurial 
coating was partially calcined. 

After this it was impoflible to entertain' 
a doubt cor^cerning the nature of this black 
powder. It was evidently mercury fuper- 
fhlogijiicafedy or which had acquired more 
phlogiflon than was neceflary to its flate of 
white running mercury. But it remained 
to be inquired whence the mercury could 
have received this phlogiflon. That it 
might have been communicated from the 
fpirit of wine in the e^fperiment mentioned 
above was probable enough, becaufe fpirit 
of wine is known to contain phlogifton in 
abundance. But it has been a maxirn with 
chcmifls, that water is incapable of form- 
ing any union with phlogifton ; and that 
befides air, it is perhaps the only fubftance 
in nature that is incapable of it. However, 
M 3 afi 

1 66 Obfervations on 

as the v/hole courfe of my experiments 
has demonilrated" the fallacy of the maxim 
with refpe6t to air, fo I think alfo it has 
already appeared from them, that neither 
does it hold good with refpe(9: to v/ater. For 
if water did not, in its natural flate, con- 
tain phlogiilon, hov/ could pure air become 
phlogiilicated (which I think I have de- 
monilrated to be the cafe when it is ren- 
dered noxious) hj agitation in it ? And if 
it was incapable of receiving more phlogif- 
ton than it naturally has, how could noxious 
air of all kinds be rendered wholefome, or 
dephlogiflicated by agitation in it ? Alfo 
that water and phlogiilon may form a tem^ 
forary union, or be mixed, is, I think, 
evident from various obfervations, as from 
what is called the empyreuma of water frefh 
diftilled -, and efpecially from the fmeU 
given to water by calcination of metajs 
over it, in the experiments recited in my 
iirft volume. I am therefore, fometimes 
inclined to think that, during the agitatioij 
of quickfilver in water, the water commu- 
nicates of its phlogiflon to the mercury, 


Mercury. 167 

The mofi: material objedion that I am 
now aware of to this conclufion is, that the 
fame water may be ufed, as far as I know, 
without end, and yet it will always retain, 
and even andiminifhed, its power of con- 
verting mercury into this black powder. 
J once agitated mercury in a quantity of 
water very many times (having nothing but 
the mercury and the water in the phial) 
and after every procefs I fhut up the water 
from all accefs of the external air; at the 
fame time that another quantity of the 
fame diflilled water, agitated with mercury 
juft as much, was alv/ays kept in an open 
vefTel j yet, after fome time, when I re- 
peated the agitation of the mercury, I was 
not able to perceive any difference between 
the effed: of the agitation in the water that 
had been confined, and in that which had 
been expofed to the air. Alfo, when I 
have examined the air confined in a phial 
over the furface of water in which mercury 
had been agitated a long time, it never 
appeared to be in the leaft different from 
the common external air, as might have 
M 4 been 

i6S Ohfefvations on 

been expecSled, if the water had been 
deprived of any portion of its proper phlo- 
gifton, and had recovered it again. For 
whence could it have been recruited, but 
from the air ? It is alfo unfavourable to 
the hypothefis above-mentioned, that water 
fliould much more readily contribute to 
the converfion of mercury into black pow- 
der when it has been feveral times ufed for 
this purpofe, than at the firfl. 

Some may, therefore, think that it is 
the calx of the mercury that the water 
feizes upon,' leaving the phlogifton as an 
over charge upon part of the remainder. 
Whichever of thefe hypotheiis is the true 
one, it is a fa6t, and certainly a very re- 
markable one, that, if the water be warm, 
though only about blood heat, no agitation 
of mercury in it will convert it into black 
powder. And alfo, if the water be ever 
fo black with the pov/der, the mere heat- 
ing of it, without any accefs of the exter- 
nal air, will make it tranfparent again ; 
the blacknefs totally difappearing both from 
the water and the mercury. If the former 
'. hypothefjs 

Mercury. 169 

hypothecs be admitted, viz. that the over- 
charge of phlogifton is communicated from 
the mercury to the water, water muft be 
of fuch a nature as to have a ftronger affi- 
nity with phlogiilon when hot than when 
cold, in which, though it be the reverfe 
of moft other fubftances, it has the fame 
property, however, with air, which receives 
phlogifton fx'om ignited bodies, when both 
the air and the ignited body mufl, of courfe, 
be equally hot. 

Or, laftly, it may be fuppofed (and fome 
obfervations that will be recited hereafter 
prove this is ad;ually the cafe in fome cir- 
cumllances) that during the agitation onp 
part of the mercury becomes dephlogiftl- 
cated while another part is fuper-phlo- 
giflicated, extraordinary as the fadt w'A\ 
be thought. 

I obferved the efFed: of warm water in 
mercury in the following manner. Sitting 
pretty near the fire, when the weather was 
cold, I found that my agitation of the 
mercury had not fo much eifed: as it had 
J3een ufed to have^ and, refleding upon 


I JO, Obferv&iions on 

the fubjeft, it occurred to me, that poffihly 
it might be the warmth of the water in the 
phial that obftru6ted it. To try this, I put 
the phial containing the water and the 
quicklilver into a pan of water, which I 
made to boil ; after which I took it out of 
the pan, and holding it with a couple of 
handkerchiefs, agitated it with as much 
violence as I poffibly could, but I found 
that I might do this as long as I pleafed, 
v/ithout producing any thing like the black 

To complete this experiment on the 
eife<5ts of heat, as foon as the whole was 
cold, I fhook the phial again, till the 
water was to appearance, almoft as black 
as ink, and placed it in the water over 
ikiQ fire ; obferving that the phial was 
completely filled with the water and quick- 
filver, and that all air was excluded, only 
leaving the ftopper rather loofe, that the 
expanfion of the water by the heat might 
not burfl; it. The effed: was that, prefently 
after the water in the pan began to boil, 
the water in the phial had recovered its 
^ tranfpa- 

Mercury^ ijx 

tranfpareucy -, and when I examined the^ 
quicklilver, there was no appearance of 
black powder upon it. The whole had 
been reconverted into white running mer- 
cury, and had united with the reft of the - 
mafs of mercury in the phial. Alfo, when 
it was cold, the blacknefs did not re-ap- 
pear j but the mercury was, in appearance, 
in the very fame ftate, as at the beginning 
of the procefs. 

This fad: being a very remarkable one, 
I repeated the experiment many times, and 
in a very great variety of ways, but always 
with the fame refult. When, indeed, I 
agitated the mercury in the fame water a 
very long time (and I once did it on pur- 
pofe a quarter of an hour, with little or 
no intermiffion, though in one minute I 
eould make the water quite opake with the 
fame degree of agitation) I have found that 
it requires a longer continuance of heat to 
make it perfectly tranfparent, and a flight 
blacknefs has remained on fome parts of 
the furface of the quickfilver. But then 
this was quite trifling compared with the 


172 Obfervations on 

quantity of black matter that lay upon it 
before it was heated, fo that by much the 
greatefl part of the phlogifton muft have 
been abforbed. 

Alfo, when I have poured the quickfilver 
off, and heated the turbid water by itfelf, 
the blacknefs has never failed to difappear. 
put fometimes a few globules of quick- 
filver would remain at the bottom gf the 
phial, fome white, and others black; but 
though the latter were more numerous, 
they were probably only fuperiicially black, 
and no agitation of the phial would ever 
give the water the turbid appearance that 
it had before ; the globules, though difr 
perfed through the water by the agitation, 
fubliding in a rnoment, and falling, like fo 
many leaden fliot, to the bottorn of the 
phial j fo that the black furface of thefe 
larger maffes of quickfilver, as they may be 
called, was very fmall in proportion to the 
furface of the infinite number of black 
molecules which conftituted the clouds of 
attenuated mercury that before had filled 


Mercury. 17^ 

the whole phial, and made all the water in 
it opake. 

That other perfons may more ealily fuc- 
ceed in this experiment, I mufl inform 
them, that I have generally made ufe of a 
ten ounce phial, about a quarter of it filled 
with quickfilver, and the reft with diftilled 
wat^f, fhaking it as violently as I can,- 
generally giving it ten or a dozen fhakes in 
quick fucceffion, in the manner defcribed 
above j and then waiting till the water and 
quickfilver be feparated from each other^ 
which gives me a fufficient interval of time 
to reft from my labour. 

The above-mentioned experiments may* 
be made, with the fame refults, by fubfli- 
tuting fpirit of wine for water. After 
agitating fome quickfilver in fpirit of wine 
till it was very turbid, I placed the phial 
containing them in a pan of water, and 
prefently after it had boiled all the black- 
nefs difappeared. Agitating it again, when 
it was hot, had no effed ; and when it was 
cold the blacknefs did not return. The 
black powder thus procured bec^ame running 


174 Obfervations 6n 

mercury wkeii it was dry, but it wag 
not fo bright as that which had been agi- 
tated in "^^ater. Letting a quantity of it 
remain fix or feven hours upon a plate of 
glafs, on the iron plate of a Bath ftove, in 
which there was a pretty good lire, it loft 
its metallic luflre and conliftence and be- 
came a white powdery fubjiance, which- was 
completely diffolved in fpirit of fait, and 
thereby appeared to be a perfect calx of 
mercury, though it was not brought to the 
flate of precipitate per fe. 

Having now advanced another ftep in my 
inveftigation of the changes of mercury, in 
palling from the fuper-phlogifiicated to the 
dephlogiflicated flate ; I went through the 
fame procefs with the black powder pro- 
cured by the agitation of mercury in water, 
covering with it the greatefl part of the 
furface of a watch glafs (which I find a very 
convenient thing for many fmall experi- 
ments) and placing it on the plate of the 
Bath ftove, very near the fire, fo that 
different parts of it might be expofed to 
different degrees of heat. The refult of 


Mercury, tyt 

tMs experiment was very latisfad;ory and 

At firft, as I have obferved before, the 
black powder became running mercury ; 
but prefently after it adhered pretty firmly 
to the glafs, and then, looking on the 
back fide of it, I found it made the moit 
perfect mirror imaginable, a better, I 
fhould think, than that which is made 
with mercury and tin. With a longer ex- 
pofure to the fame heat it loft its metallic 
luflre, and became a white powdery fub- 
Jlance ; and with more heat it affumed a 
brown colour. Yet a quantity of this brown 
matter, though, I doubt not, it was an ap- 
proach to a proper percipitate per fe, was 
not wholly diffolved in fpirit of fait, fo 
that the calcination had been imperfect. 

It was pleaiing to obferve the mercury 
within fa fmall a compafs as that of a watch 
glafs, in three of the ftates above-men- 
tioned, viz, the white metallic ftate, the 
white calx, and the brown, or the dephlo- 
gilUcated ilate. On a. larger plate of glafs 


iy6 Obfefvations • on 

all the four Hates might have been exhibit- 
ed in their natural order, the black powder, 
or the fuper-phlogifticated ftate, preceding 
the reft. The order in which thefe differ- 
ent ftates of the mercury fucceed each 
other is a proof of the hypothecs I have 
advanced on the fubjed:. 

I {hall now^ mention fome other circum- 
ilances relating to the agitation of water in 
mercury, the caufes of which I own I do 
not underftand, and fome of them feem to 
militate againft the hypothecs advanced 
above. But this gives me no particular 

Indeed the greateft difficulty arifes from 
the fadt mentioned above, viz* that water 
which has been often ufed in this procefs 
has a much quicker and greater effed: than 
water that is ufed the firft time. This is 
more efpecially the cafe with water that has 
been diftilled a long time. This certainly 
proves, that fome change has been made 
in the water as well as in the quicklilver. 
But if the water communicates phlogifton 


Mercury » ijy 

to mercury, it might be expelled that it 
would give it more readily at iirfl thaa 

Alfo, if it be water that communicates 
the phlogifton to the mercury, it might be 
expeded that water frelh diftilled would 
have, a greater eifedr, on account of the 
empyreuma that it is fuppofed to acquire 
by diftillation, and which is known not to 
kave it of a confiderable time. And, in 
general, I have found that water freih 
diftilled fooner becomes turbid in this pro- 
cefs than water that has been long diftilled, 
but not fo foon as water that has been 
often ufed for this purpofe. Alfo when I 
have re-diftilled water that has been much 
ufed in thefe experiments, it has been as 
readily affeded as before the fecond diftilla- 
tionj but with this difference, that the 
black powder has been much longer in 
fubfiding than it had been before. 

I have often found great differences in 

water in this refpedt. In general, if the 

water has been long diftilled, and frequently 

ufed, the depofit will be completely made 

N in 

lyS^ Obfervations on 

in a few minutes ; whereas I have fome-* 
times found that the water has not become 
clear (uling the fame mercury) in three or 
four days. And even when the blacknefs 
has difappeared, a white cloudinefs will 
remain I do not know hoW' long. 

I found fome difference, but not fo much 
as I had expeded, between water diftilledwitU 
a gentle heat without boiling, and water that 
was made to boil violently during the diflil- 
lation, though both were diftilled in glafa 
veflels. They both became turbid pretty 
foon, and the quantity of black powder 
was nearly equal from both, in the fame 
time; but that which had been haftily 
diflilled depofited its fediment in about 
ten minutes, whereas the other had done 
it very imperfedly in an hour. I would 
not, however, be politive that a fecond 
experiment of this kind would have a 
fimilar refult, as this circumftance may 
depend upon a eaufe not yet inveili- 


There was fomething remarkable in thfc 

phenomena that, occurred in ufmg a, quan*- 

2 tity 

Mercury. ^179 

tity of water frefh diftilled in a copper 
Veflel, and a pewter worm, in the common 
way ', but in which fome elder Jlowers kad 
been diftilled about a year before, fo that the 
water had a flight fmell of it. But whether 
this circumftance has any thing to do with 
what I am going to defcribe, I cannot 

Agitating the quickfilver in this water, 
it prefently became very turbid, but the 
fediment was not depolited in a week, or 
indeed completely, in a fortnight ; and then 
the water retained a white cloudinefs. But 
thq mofl remarkable circumflance was that, 
in agitating the mercury in this water, the 
whole mafs was prefently divided into 
fmall globules, not larger than the fmallefl 
pins heads, and did not very readily unite 
again. Several times I have found that the 
mercury thus divided would choak up the 
mouth of the phial, which is about half 
an inch wide 3 fo that, holding it perpen- 
dicularly, it v/ould not run out at all in 
feveral feconds. It has even required fhaking 
to get it all out. It has then exhibited a 
fmgular and beautiful appearance in the 
N z cup 

i8o Obferijattons on 

cup into which the phial was emptied, 
whereas the very fame quicklilver agitated 
in other water, immediately before, and 
after, has been attended with no other thani 
the common appearance. It was alfo re- 
mai-kable, that this divided mafs of mer- 
cury, after the moft violent agitation in the 
water, fell inftantly to the bottom, like a 
quantity of leaden ihotj whereas, in general, 
as I have obfcrved, the mercury and water 
^^t intangled in fuch a manner, that they 
do not intirely feparate in feveral feconds. 

Imagining at firft, that the power of re- 
union, in the divided mercury, might per- 
haps have been impaired by fome efFe<5l"of 
the fmall remains of the elder water, mixed 
with the frefh diflilled water in which it 
was now agitated, I made trial of mint 
water, but without any fuch eifed:. A con- 
fiderabie time afterwards, however, I found 
other methods of producing the fame eifedl, 
and even in a much more remarkable man- 
ner, though I am ftill at a lofs to account 
for the proximate caufe of the phenomenon. 

Having a phial containing fome water 


Mercury, 1 8 1 

imperfedly impregnated with vitriolic acid 
air, and likewife a quantity of the quick- 
lilver on which the impregnation had been 
made, I found that when they were agi- 
tated together the whole mafs' of quick- 
lilver was divided into fmall globules, and 
that they did not perfe(5tly reunite after 
being at reft a day and night. But when 
the phial was heatedy they united as readily 
as in common water. When it was cold 
again, the mercury was divided by agita- 
tion, and continued divided, but not quite 
fo much as before. 

This being an acid liquor, I made trial 
of other acids j and I found the fame efFe(fl 
with oil of vitriol -y but the divilion of the 
mercury into fmall globules did not con- 
tinue very long, and when it was hot the 
eifedt was inconliderable. But the moft 
complete eiFe<5t of this kind is produced by 
'vinegar. A very little agitation of mercury 
in this acid divides it into the fmallell 
globules; and they continue without any 
apparent difpofition to reunite even whea 
very hot. While this divide4 mercury is 
N 3 ia 

1 82 Ohfervatwns an 

in the vinegar the globules may be poured 
from one part of the phial to the other 
exadtly like fine dry fand, and they exhibit 
a fingular and beautiful appearance. All 
the vinegar muft be evaporated by heat be- 
fore thefe globules w^ill unite. 

Mercury agitated in fpirit of fait, and 
alfo in a volatile alkaline liquor, was not 
attended with any remarkable appearance of 
this kind. 

I have fometimes been much amufed 
with another fingular appearance. In agi- 
tating mercury in vyater, efpecially vi^hen 
frefh diftilled (when there has not been a 
bubble of air in the phial) large balls of 
various fizes, fome not lefs than half an 
inch in diameter, have not only rolled 
upon the furface of the mercury, after it 
had completely fublided, and continued 
there a confiderable time, but have floated 
up and down in the water, like fope bub- 
bles in the air. Thefe bubbles muft con- 
fift of water inclofed in a thin pellicle of 
mercury, for when they buril, nothing 
vifible comes out of them, and the 


Mercury, 183 

quantity of mercury about them is not 
enough to be perceived in its defcent 
through the water afterwards. 

I may alfo mention, as another pleafing 
phenomenon in thefe experiments, the 
viewing of a fmall quantity of the moiften- 
ed black powder with the microfcope. For 
in the inilant that it becomes dry, the 
colour changes y and in fo fmall a quantity 
the change is almofl: inftantaneous, fo that 
the black globules immediately become 
white, and beautifully polilhed ones. 

In order to afcertain what change had 
taken place in the water in which mercury 
had been agitated, I diftilled a quantity ©f 
it, and the refult of the experiment is 
rather in favour of the water having feized 
upon the calx of the mercury, than of its 
having parted with any phlogiftoi) to it. 

After the diHillation I found a ponfider;- 
able quantity of a yellov/ifh refiduum, 
which, when it was expofed to heat, on a 
plate of glafs^ became quite blacky ar)d 
with more heat was brown. Being expofed 
to the open air, it became very moiH:. Put- 

N 4 '. .^TO 

184 Ohfervations on 

ting it, after this, into a glafs tube, and 
expofing it to a red heat, a whitifh mat- 
ter fublimed from it, and coated the inlide 
of the tube at fome diftance from it. This 
matter was not diflblved by fpirit of fait ; 
and therefore, though I think, from the 
appearance of it, it was probably a calx of 
mercury, it mull have been an imperfed: 
one, containing a confiderable proportion of 


Of the BffeSi of , long continued Agitation 
on ^lickjiher. 

N order to give quickfilver, in con- 
jund:ion with various other fub- 
fiances, a much more, and a longer con- 
tinued agitation, than I was able to give 
them by fliaking the phials that contained 
them in my hand, I got a ftrong wooden 
box, 2J\^ had a contrivance in a neigh- 
bouring mill to have it agitated whenever 
the niiii was in motion, v^^hich I found was, 


Mercury, 185 

at a medium, about twelve hours in 
twenty- four. There was fome diiFerence 
in the circumftances of the quickfilver in 
all the veffels, and I (hall give a brief ac- 
count of what I obferved with refped: to 
them. The box was made up, and fent 
to the mill on the 9th of December 1777, 
and the contents of it were examined on the 
loth of May following. 

No. I. An eight ounce phial with a 
ground ftopper containing a pound of 
quickfilver, except 5 dw. which it had lofl 
by frequent agitation in the fame diftilled 
water with which it was now fhut up, the 
water being about four times the bulk of 
the quickfilver, marks being made upon 
the phial with a file, to denote the height 
of the water and of the quickfilver . When 
it was examined, the water appeared to 
have been diminifhed one feventh in its 
bulk, having poflibly made its efcape by 
the fide of the flopper. The quickfilver 
had lofl eighteen grains, which was pro- 
bably the weight of the black powder that 
was formed in it ; but y^^hat I thought the 

1 86 Obfervations on 

moft extraordinary circumftance, was that 
the bottom of the phial was tinged with 
a deep orange colour. Not willing to put 
other water, or other quickfilver into this 
phial, I made no other trial of the air, than 
by letting a fmall candle down into it, and 
I obferved that, to all appearance, it burned 
very well. 

No. II. A glafs tube hermetically felled, 
containing quickfilver and diftilled water, 
which had been agitated one month before, 
in confequence of which a good deal of 
black powder had been formed. This had 
received an increafe of black powder, and 
part of the vefTel was coated with the 
brown matter above-mentioned. 

No. III. A three ounce phial with a 
ground flopper, containing quickfilver and 
water diililled in glafs, about twice the 
bulk of the quickfilver. The furface of the 
mercury was well covered with black 
powder, and befide this, a good deaj ad-» 
hered to the bottom of the phial, and was 
alfo difpofed in fi:reaks almofi: furrounding 
it, in the middk of that part of the phial 


Mercury. i2j 

that had been occupied by the mercury. 
This black coating, viewed in a certain 
light, appeared of a dirty orange colour. 
A candle burned in the top of the phial. 

No. IV. A three ounce phial with a 
ground flopper, about one fifth filled with 
quickfilyer, without water. The quick- 
lilver was well covered with black powder, 
and alfo a great part of the infide of the 
phial. A candle burned in it very well. 
Whether this quickfilver was perfectly pure 
J cannot abfolutely fay. If it had, I can 
hardly think there would have been fo much 
black powder; and yet had it been very 
impure, the air within the phial would 
have been phlogifticated. If the quick- 
filver was pure, the agitation muil have dif- 
pofed one part of the quickfilver to part 
with its phlogifton, and another part of 
the fame mafs to have received it, which 
the circumilances in the other cafes rendex 
probable -, and if we admit this hypothefis, 
we Ihall be relieved from the fuppofition 
of the water, in the former experiments, 
communicating the phlogifi:on to the 


jS8 Obfervafions on 

quickfilver, in order to the formation of 
the black powder. 

No. V. A two ounce phial with a ground 
ftopper, containing quickfilver and fpirit of 
wine, the latter one and a half more in bulk 
than the former. The fpirit was a little 
diminiihed in bulk, the mercury had more 
black powder upon it than there was in the 
phial containing quickfilver and water, 
and a compa(5t body of this black powder 
covered one fide of the phial j beginning 
at the furface of the fpirit, and reaching to 
the top. 

No. VI. A tall green glafs phial, with 
a little quickfilver and diflilled water, and 
a green glafs peflle, weighing 9 dw. 4 gr. 
The phial was coated with black powder, 
a candle burned in the phial, and the 
peftle weighed 9 dw. ^ gr. 

No. VII. A tall green glafs phial, con- 
taining quickfilver 7 oz. odw. 12 grs. 
lead 2 dw. with diftilled water. A candle 
would not burn in the phial, it was coated 
with black powder, but there was very 
little of it, notwithflanding the mafs of 


Mercury. i g^ 

mercury and lead had not loft quite two 
grains of their weight. 

No. VIII. A tv/o ounce phial with a 
ground ftopper, containing mercury and oil 
of turpentine, about one and a half as much 
as the bulk of the mercury. In this there 
was no feniible change. 

I have obferved that, in the phial in 
which quickfilver only had been agitated, 
and alfo in another which had contained 
both quickfilver and water, there was a 
quantity of brownifh matter adhering to 
the glafs. Had this matter been a calx of 
lead, mixed with the mercury, the air 
within the phial would certainly have been 
phlogifticated. Befides I am pretty fure 
that I had taken fufficient care to have this 
mercury pure. I am therefore inclined to 
think, notwithflanding the peculiar man- 
ner in which it was produced, that it was 
xh^ precipitate per fe. The few obfervations 
that I did make upon it are all in favour of 
this fuppofition. When I expofed it to the 
heat of the fire, it became of a deep and 
proper orange colour, and when I expofed 


I go Ohfefuations on 

the phial that con tained it to a great degree 
of heat, but not fufficient to melt the 
glafs, the air within the phial was found 
afterwards to be rather better than common 
air, though not fo much as that I could be 
abfolutely certain the feeming difference 
might not have been owing to fome acci- 
dent in making the experiment. 

But what I think the moil nearly deciiive in 
favour of this hypothecs is, that the phe- 
nomena attending the folution of this fub-» 
ilance, and of the precipitate perfe, in fpirit 
of fait, are, in all the refpeds in which I 
compared them, the very fame. This orange 
coloured matter in the phials was inflantly 
dilfolved by the fpirit of fait, which, from 
being of alight ilraw colour, became colour- 
lefs, like water; and when it was afterwards 
evaporated, it left a perfedily white fubftance 
behind. In all thefe particulars the folu- 
tion of a fmall quantity of precipitate perfi 
was attended with the fame appearances* 
Alfo when a little of both the rejidua was 
laid on a thin plate of glafs, and expofed 


Mercury, tgn 

to the heat of a candle, they were evaporated 
in a white fmoke, exacStly alike. 

Admitting this fubftance to be a true 
percipitate per fey or a complete calx of mer- 
cury, we may perhaps explain the formation 
of the black powder produced by the agi- 
tation of mercury in water, by fuppofing 
that while one part of the mercury is fuper- 
phlogiflicated, and becomes black, another 
part of the fame mafs is dephlogiflicated 
or reduced to a calx, which is firft white, 
but would in time alTume an orange colour. 
,And that the water diiTolves a part of this 
calx, feems probable from the obfervation 
I made on the depofit made by it when ic 
was evaporated. 


1 92 Obfervatiom oft 


Of the Conjittution of dephlogtfitcated Air^ 
and a Review of the Obfervations relating 
to it. 

ON the fubjed of dephlogijiicated air, 
I am happy to be able to give my 
readers much more light than they, or I, 
could have any reafon to expecft from my 
laft publication relating to air, efpecially 
with refped: to the fundamental articles of 
the origin, and confequently the conjiitution 
of it, and therefore of the atmofpherc in 
which we live. As it fometimeS amufes 
myfelf, it may perhaps amufe others, to 
look back with me to the feveral fleps in 
the a(5tual progrefs of this inveftigation, 
fome of which I over-looked in my laft 
account of it. 

From a view of my different publication^ 
relating to air, it will appear, that I was, 
in fad:, pofTelTed of this remarkable 
fpecies of air at a very early period in my 
inquiries, as may be colleded from my 


Dephhgljilmted Air, 193 

ilril: papers fent to the Royal Society, and 
before I formed them into a volume. For 
the peculiar charadiers of this kind of air will 
be found in my defcription of that which 
I extraded from fait petre, and alfo of that 
frorn alum. See my Obfervations on Air, 
Vol. I. p. 155. I there fay *' All kinds 
** of faditious air, on which I have yet 
*^ made the experiment^ are equally noxi- 
^' ous, except that which is extrad:ed from 
** fait petre, or alum ; but in this even a 
*' candle burned juft as in common air. 
** In one quantity which I got froni fait 
** petre a candle not only burned, but the 
f* flame was increafed, and fomething w^§ 
*' heard like a hijjtng, limilar to the de^ 
*' crepitation of nitre in an open fire. This 
*' experiment was made when the air was 
*' frefh made, and while it probably con- 
•* tained fome particles of nitre, which 
** would have been depofited afterwards/* # 
This hijing, however, was certainly owing 
to the avidity with which this pure air 
feized upon the phlogiilon of the bodies 
ignited in it ; and that property would not 
O have 

194 Obfervations on 

have been loft by mere keeping, as I then 

This air, it appears that I was in pof- 
feffion of before the month of November 
1771. For in November 1772 I mention- 
ed my examining a quantity of air which 
had been extracted from fait petre above a 
year before, and which I fuppofed to have, 
by fome means or other, become noxious, 
but to have been reftored to its former 
wholefome ftate, fo as to efFervefce with 
nitrous air, and admit a candle to burn in 
it, in confequence of agitation in water. 
" This feries of fadts," I then fay, p. 157 
** relating to air extracted from nitre appears 
** to me to be very extraordinary and im- 
*' portant ; and in able hands may lead to 
** confiderable difcoveries." Confiderable 
difcoveries, indeed, have been made On 
the fubjed: fince that time, but not in con- 
fequence of thefe iirft hints falling into 
able hands ; for the whole has been a fuc- 
ceffion of very extraordinary accidents.' - 

So far was I from having a right idea of 
the nature of this air; or rather, {o far 


Dephlogifticated Air* 19^ 

wasi*I from preferving a right idea of it 
(for it is evident that, at thefirft, Iconfidered 
it as having the valuable properties of com- 
mon air, at leaft) that when I republifhed 
my firfl volume, which was about a year 
afterwards, I added a note to the above 
ficcount of air extracted from nitre, in 
which I fay, ** It is probable that, though 
" a candle burned even more than well in 
V this air, an animal would not have lived 
*' in it, though, at the time of my iirfl: 
** publication, I had no idea of this being 
** poffible in nature." This doubt was 
fuggefted by my having afterwards brought 
nitrous air into a ftate in which a candle 
burned in it with a natural, or even an 
enlarged flame, though it was flill noxious 5 
not having attended to the difference be- 
tween the appearance -of that enlarged fame , 
and that of the peculiarly vivid jiame. of a 
candle in dephlogifticated air, in confequence 
of the experirnents having been made at a 
great diftance of time from each other. 

In this ftate the matter refted till Auguft 

17741 when, without any particular view, 

O 2 except 

ig6 OBfervations on 

except that of extracting air from a variety 
of fubftances by means of a burning lens in 
quickfilver, which was then a new procefs 
with me^ and which I was very fond of, I 
cxtradted this air from the precipitate per fey 
from the Qovamovi. red precipitate, 2ind with 
a mixture of fixed air, from red lead alfo. 
See my fecond volume, p. 34, &c^ * 

In this air, I obferved that a candle 
burned with a remarkably vigorous flame j 
but I did not even then attend to the diiFer- 
ence between this appearance, and that of 
the enlarged flame above-mentioned. This 
air, however, having been procured with- 
out nitre, puzzled me exceedingly, and I 
Gould not even believe that my precipi- 
tate w'as a right preparation of the kind, 
till I procured a quantity of Mr. Cadet at 
Paris, when I was there in the October 
following. But from this preparation, in 
the March following, as will be iztw in 
my fecond 'uolumef p. 40, I got air which I 
was gradually fatisfied had all the properties 
of common air, only in much greater per- 
fe(9:ion, fo as to be intitled (according to- 


Dephlogifi'kated Atr. 197 

iBy idea of purity and impurity with refpedt 
to air) to the name of dephlogiflicated air, 
which, for that reafon, I gave to it. 

My idea of this kind of air, and con- 
fequently of atmofpherical air (which is the 
fame thing, but in a ftate of inferior purity) 
confifting of earth and fpirit of nitre arofe 
in the following manner. Having procured 
inflammable air from various fubftances by 
the help of the marine acid air, and being 
able to render this inflammable air fit for 
refpiration, I conjectured that one ingredi- 
ent in the compofition of this air was that 
acidj, and that the great mafs of air belong- 
ing to this planet might have been originally 
fupplied by volcano's, which I fuppofed to 
throw out a great quantity of inflamma- 
^ble air. 

Having now got pure air from r&d lead, 
which I fuppofed to have acquired its power 
of yielding it, in confequence of having 
imbibed fome acid from the air.j and hav- 
ing fortunately procured a quantity of red 
lead in fuch a ftate that it would not of 
kfelfyiQld any, or very little air» I moifl:ened 
O 3 feparate 

19S ■ Obfervations on 

feparate portions of it with each of the 
three mineral acids, in order to determine 
which of them it was that it had imbibed. 
And prefently finding that the portion 
which had been moillened with the nitrous 
acid yielded plenty of the fame kind of air 
that red lead in its natural ftate yields, and 
that the portions which had been moiftened 
with the other acids yielded none at all, I 
had no doubt but that it was the nitrous 
acid, that it had imbibed before. I was 
farther confirmed in this opinion, by being 
able to procure dephlogifticated air by the 
mixture of nitrous acid with any kind of 
earth whatever 3 fo that there is not, I 
believe, any fubftance in nature, which I 
am not able, by the help of this acid, to 
convert into air. 

Such were my ideas at the time of the 
publication of my fecond and third volumes 
on the fubjedt of air. But I have fince 
feen reafon to fufpe^t that hypothefis, plau- 
iible as it appears 5 and at prefent I am 
, inclined to think that, though, befides 
earthy fome acid enters into the compofition 


Dephlogtfikated Air. 1 9^ 

of air, it is not necefTarily the nitrous acid, 
but, in fome cafes, the 'vitriolic -, or at leaft, 
in the proceffes by which this air is pro- 
cured, they are converted into one another, 
or into fome other acid, or fubfhance, 
that bears aft equal relation to them both ; 
and that, in this ilate, common to them 
both, it exifts in the atmofphere. 

Indeed, fome of my late experiments 
would lead me to conclude, that there is 
no acid at all in pure air, but that thofe 
which I made with the folution of mercury 
in fpirit of nitre, mentioned in the preface 
to my third volume, feem to be decisive in 
favour of the contrary. For though, in my 
opinion, they prove that fome earth enters 
into the compolition of air, or, at leall:, 
that earth is dilTolved in air, yet the a<5lual 
weight of the air procured in the procefs 
greatly exceeds the lofs of weight fuftained 
by the mercury 3 fo that what the air 
weighs more than that lofs it mufl- necef- 
farily, as I think, have derived from the acid. 

The new fad:s that have occafioned this 

iiud:uation in my opinion on this fubjecft 

O 4 are. 

j^oo Obfervixtions dn 

are, that pure air is extraded frdJn fub- 
ftances combined with the vitriolic acid, 
from various mineral fubflances, vt^hich 
we do not know to have had any communi- 
cation with the atmofphere, and other re- 
markable fads of a iimilar nature. Thefe 
new faBs I fliall exhibit, as nearly as I can^ 
in the order in which they occurred to me* 
I was led to thofe relating to the vitri- 
olic acid, and mineral fubftances, in a 
courfe of experiments made with no other 
view than limply to try what kind of air, 
and in what proportion, fuch fubftances 
as I could conveniently meet with would 
yield. And it is fome thing remarkable, 
that though I have mentioned my having 
got pure air from Roman vitriol, in one of 
the moft accurate of all my procefTes, I 
fhould not have given more attention to 
the obfervation, and have purfued it far- 
ther ; but that, after fo long an interval of 
time, I fhould have been brought partly by 
accidents refpeding my own experiments, 
and partly by the affiftance of others, into 
the very track which my own former 


Dephlogijikated Air. 201 

obfervations could not have failed to 
bring me. 

The difcovery of the vitriolic acid con- 
tributing to "the production of dephlogifti- 
cated air properly belongs to Mr. Landriani, 
and I had the communication of it from 
him. He informed me, that he had pro- 
cured this kind of air both from turbith 
mineral, and alfo from corrojive fiiblimate. 
The latter I tried immediately upon the 
receipt of his^ letter, but I was unable to 
procure any air from it ; and finding that 
nitrous acid was fome times ufed in the 
preparation of turbith mineral, I imagined 
that he might poffibly have made ufe of that 
kind of preparation, and that with refped: 
to the corrofive fublimate, he had made 
fome mijftake that I could not difcovef. I 
therefore contented myfelf with purfuing 
the track that I was then in; and having 
firft found dephlogifticated air in manganefe, 
and other mineral fubftances, I after- 
wards, in continuing the fame procefs, with 
the fame general and indiftind: views pro- 
cured it ixov£i green copperas, and at length 


202 Obfervations on 

from other vitriolic falts ; and it was not 
without great difficulty that I could be 
brought to believe that it was the pure 
vitriolic acid that was the proper caufe of 
tliis efFe£t. 

In this introdudtory fedion I would like- 
wife obferve, that, in making thefe experi- 
m.ents, I generally made ufe of fmall bellied 
retorts, containing about an ounce of 
water, with very long and narrow necks, 
viz, of eighteen or twenty inches, put- 
ting the fubftance on which I made the 
experiment into them, and then expoling 
them to a red heat, either in fand, or over 
a naked fire, while the neck of the retort 
was plunged in water or mercury. 

The reafon why I had no better fuccefs 
whe%i I endeavoured to procure air from 
many of the fame fubfhances before, was 
either my trying them only in very fmall 
quantities, upon quicklilver, with the heat 
of a burning lens, or uling a gun barrel, the 
phlogiflion from which contaminated the 
air. I did, indeed, fometimes make ufe 
of a phial with a ground Hopper and long 

tube ^ 

Dephlogifticated Air. 205 ' 

tube ', but this being an expenfivc inftru- 
ment, I ufed it very rarely, and it was more 
liable to accidents than the long retorts, 
which are reafonably cheap, efpecially when 
made of green glafs ; which is, at the fame 
ti^e the beft in other refped:s, as con- 
tainir 3- no lead, and able to fuftain a greater 
degree of heat. , 


Of the RxtraSfi'on of Dephlogifticated Air 
from fever al Mineral Subfances. 

WI T H no other view than the general 
one mentioned above, vt2^. to try 
what kind, and proportion of air, different 
fubflances would give in a red heat, I en- 
tered upon the examination of manganefe,- 
about which much has been written, but 
of which much yet remains to be invefli* 
gated by chemijfts. Of this I procured a 
quantity finely pounded -, and from an ounce 
of it I got, in a red fand heat, forty ounce 
meafures of air, part of which^, in every 


:lo4 Ohfervaftom en 

portion, was fixed air, and at firft almoft 
wholly fo ; but four fifths of the laft was 
the pureft dephlogifticated air. Even the firfl 
that came over, which was the common 
air, in the veflel was not in the leaft 
dephlogifticated. The manganefe had loft 
li. dwts. of its weight, and was not to be 
diftinguifhed in colour (which was black) 
from what it had been before, A con- 
iiderable quantity of water came over 
during thi« procefs. 

That Manganefe fhould givcjixed air did 
not at all furprize me ; fince there are few 
earthy fubftances that do not contain more 
or lefs of it; but I did not at all exped the 
dephlogifticated air y as, before I had ima- 
gined that the nitrous acid was necelTary to 
the produd:ion of it, or at leaft the influence 
of the atmofphere, which I fuppofed might 
depofit the acid that entered into its com- 
pofition, and which I concluded to be the 
nitrous. On the contrary here was pure air 
from a fubftance which, for any thing that 
appeared, had always been in the bowels of 
the earth, and never had had any commu- 
Z nication 

Dephlogiftkated J^r, 205 

jiication with the external air j and yet it 
exactly refembled red lead, both in yielding 
iixed air, and dephlogiffcicated air ; and it is 
known that red lead, like the precipitate 
per fe cannot be made but in conta^ 
with the open air. 

In order to fee how much more air this 
calcined manganefe would yield with ipirit 
of nitre, I moiftened it with that acid -, and 
in a red fand heat got from it about thirty 
ounce meafures of air, part of which, at 
the beginnings was fixed air, but not after- 
wards. The refiduum was at iirft ilrongly 
nitrous, but at the laft two thirds of the 
whole was pure dephlogifticated air. The 
glafs veiTel in which the experiment was made 
had fome black matter adhering to it, from 
'a former procefs ; and this might pofiibly 
have contributed to the produd:ion of the 
nitrous air, and confequently to the diminu- 
tion and depravation of the dephlogifticated 
air. The mixture was made with con- 
fiderable heat, and the fubflance was black 


2.0 6 Obfef^ations on * 

To fee what alteration the mixture of 
nitre would make with the manganefe (a 
procefs which I went through with a variety 
of fubilances, in order to find a cheap method 
of procuring dephlogiilicated air) I mixed 
one ounce of the manganefe, and half an 
ounce of nitre, when I got io8 ounce 
meafures of air, the fixed air about the 
fame quantity as before, and the refl de- 
phlogiilicated air. 

I next made trial of fome lapis calaminarisy 
firft pounding it very finely, then putting 
an ounce of it into one of the fmall long 
necked retorts already mentioned, and with 
a red hot fand heat I got from it 306 ounce 
meafures of air ; and making allowance for 
the lofs of air in changing the vefiels in 
which I received it, &;c. I believe I may 
ilate the whole produce at 316 ounce mea- 
fures, the whole of which was fixed air, 
except four ounce meafures 3 and, what I 
did not at all exped;, the refiduum, after 
the fixed air had been extrafted from it by 
water, appeared to be nearly as good, as 


Dephlogtjlicafed Air, 207 

common air. For one meafure of it and 
one of nitrous air occupied the fpace of 
i-L meafures. Had the proper refiduum of 
fixed air been well extracted, the remainder 
would probably have been dephlogifti- 
cated air. What remained of the 
lapis calaminaris weighed 1 3 dw. 6 gr. and 
had a lighter colour than before. This 
produce of air I took at different times, but 
the refiduum of the lafl; portion was but 
little better than that of the firft. 

From this experiment it appears that 
lapis calaminaris, as well as manganefe, re- 
fembles, in fome degree, red lead, which 
of itfelf, by means of heat only, yields 
both fixed air and dephlogifticated air, 
only a much fmaller proportion of the 

In order to obferve whether the addition 
of fpirit of nitre would make any change 
in the produce of air, I moiftened another 
ounce of it with that acid ; and in a glafs 
veflel, and with a red heat as before, I got 
from it 244 ounce meafures of air, the 
•fculk of which was fixed air, but twelve 

- . 1 ounce 

20 S Ohfervatkns on 

ounce meafures were not abforbed by water, 

and appeared to be dephlogiflicated air. 

It appears from this experiment, that the 
ipirit of nitre, befides contributing to the 
produdion of dephlogifticated air, as ufual, 
contributed alfo to the produdion of a 
large quantity of fixed air, which favours 
the hypothefis of fixed air being a mode- 
fication of the nitrous acid. It will be 
found, however, in the courfe of this 
work, that it is not this acid only, but the 
vitriolic acid alfo, that contributes to the 
formation of fixed air, as well as of dephlo- 
gifticated air. iV. 5. The fpirit of nitre 
made no effervefcence, and produced no 
heat in mixing with the lapis calaminaris. 
It alfo made no change of colour in it, and 
a very little of the acid was fufficient to 
make it fenfibly moift ; in all which re- 
fpeds it diifers very remarkably both from 
;:ed lead, and from manganefe. 

I next proceeded to the examination of 
the mineral fubftance called wolfratjii with 
a good fpecimen of which the Rev, Mr. 
Townfend had been fo obliging as to 


T>ephloglJilcated Air, 209 

fupply me, from the mines of Cornwall. 
This I pounded, efpecially the black part 
of it, and I treated it, in all refpedts, as I had 
done the lapis calaminaris. But with the 
fame procefs I procured from an ounce of 
it, not more than about an ounce meafure 
of air, a little of which was fixed air, but 
the remainder was about the ftandard of 
common air. It required a great and long 
continued heat to extract this air, and I had 
nearly defifted from the procefs before any 
of it came. After the procefs the wolfram 
was, to all appearance, the fame as before. 
Perhaps a greater degree of heat, in veffels 
proper for fuftaining it, would have pro- 
duced a greatser quantity of air. 

Thefe experiments fuggeiled to me that, 
poflibly, the expullion of dephlogiflicated 
air from thefe, and other mineral fubftances, 
might affifl in fuftaining fubterraneous fires. 
For phlogifton fet loofe in the dilTolution 
of all bodies by ignition muft be received 
by fome other fubftance, as it is not a 
thing that, as far as we know, can exift, 
except in combination with other fub- 

P ilances 

tiO Obfervations on 

ftances -, and we do not know of any thing 
that can combine with it fo readily as air j 
and therefore we find that nothing can 
burn but in contact with air, and with, 
change of air. 

When, indeed, phlogiflon is fet loofe in 
the putrefactive procefs, air is not abfolutely 
neceffary. For, in that cafe, it may be 
communicated to water, and probably to 
other fubftances fluid or folid. It does not, 
therefore, certainly follow, that there cark 
be no combuflion without air, though it 
be probable -, becaufe phlogifton may be 
able to efcape without the help of air in 
one way, though not in another. The 
folution of the phenomena of fubterraneous 
fires would certainly, however, be much 
eafier on the fuppofition of their fupplying 
their own pabulum, by means of dephlogifhi- 
cated air, contained in fubfiances expofed 
to their heat. I therefore defired Mr. 
Landriani, who, being in Italy, had a good 
opportunity of making inquiries on the 
the fubjedt, to inform me whether any af 
thofe fubilances and particularly ??ianganefe, 
* be 

T)ephlopJiicated Air. lii 

be found in their volcanos ; and his an- 
jRver makes it rather probable that thofe 
fires are, in part, fuflained by this means. 
The extraft of his letter, tranflated from 
the Italian, is as follows 

** With refped: to what you defire to be 
** informed of^ concerning the volcanic pro- 
** diiSiions, there is found in the zolfatara 
•* of Pozzuolo a great quantity of martial 
*' vitriol'^ but I do not know that there is 
** any manganefe, or lapis calaminaris, 
*' found there* The Abbe Jortis, who has 
*' lately examined the extinguiihed volcano 
'* of Verona, aflures me that, befides mar- 
** tial vitriol, he has found a quantity of 
** manganefe there. Sig. Volta, having re- 
** peated the experiments that I comm.u- 
** nicated to him, has lately informed me, 
** that he has found dephlogiflicated air in 
" calcined roclje alum, a fubflance which 
** is found in great quantities in all vol- 
** canos ; fo that it is out of doubt, that 
*^ fubterraneous fires are continually fed 
with dephlogifticated air, dillodged from 
fubflances proper for fupplying it»" 

P 2 It 


212 Obfervations on 

It is very probable, that other mineral 
fubftances may contain dephlogifticated air 
as well as thefe ; and it is certainly very 
well worth while to add this procefs to the 
chemical analyfes of them. Whether the 
fubftance be converted into air, or whether 
it contain the air, in a condenfed or com- 
bined ftate, like fixed air in chalk, it is ftill 
of importance to know what kind of air 
they may be made to yield by heat -, and 
in time we may be able to afcertain the 
true origin of fuch air. It is alfo of con- 
fequence in order to difcover the ealiefl: and 
cheapeft method of procuring dephlogifti- 
cated air in large quantities -, fpirit of nitre, 
or even crude nitre, being expenfive arti- 
cles. And though, oil of vitriol be much 
cheaper, it will be feen that the quantity 
of dephlogifticated air procured by means 
of this acid is not conliderable, except 
from mercury, which is alfo a dear article. 


Dephhgijitcated Air. 213 


Of the ProduSiion of dephlogifiicated Air 
from the Vitriolic Acid and Iron. 

AS I have been, perhaps, more than any- 
other perfon, indebted to what are 
commonly call accidents (I mean with refpecSt 
to US', for, in the general plan of nature, 
and with refped: to that great Being who 
conduces and appoints every thing, there 
cannot be any fuch thing as accident) fo 
have I been very often prevented by other 
accidents from making valuable difcoveries, 
to which I had made near approaches. This 
was remarkably the cafe with refped; to the 
production of dephlogifiicated air from fub- 
ilances containing the vitriolic acid. For 
had I, in what I improperly fuppofed to 
be an experimentiim crucis, made ufe of the 
calx of perhaps any other metal befides lead, 
on which the vitriolic acid has no proper 
action, I could not have failed to hit upon 
what the better genius of Mr. Landriani 
P 3 brought 

214 Obfervations on 

brought him acquainted with. Having, 
as I obferved before, got a quantity of red 
lead which was in a ftate to give little or 
no air of itfelf, I got pure air from it, in 
great abundance, by means of the nitrous 
acid, but none at all by means of the vi- 
triolic or marine acids. I therefore con- 
cluded, that the nitrous acid, and not ei- 
ther of the other mineral acids, enters into 
the compofition of dephlogifticated, or at- 
mofpherical air. 

Mr. Keir, who has given us an excel- 
lent tranflation of Mr. Macquers Chemical 
DiBionary, with very valuable fupplemental 
notes, in a very ufeful Treatife on Gafes 
(for fo he chufes to call the different kinds 
of air) has fuppofed that the oil of vitriol 
really contributes to the produdlion of de- 
phlogiiHcated air from Fed lead. But he 
does not feem to have attended to the 
quantity of this kind of air that red lead 
will yield by heat only, without any acid ; 
and after repeating the experiment with the 
greatefl attention, I do not find that any 
more air can be procured from the red 


Dephlogijikated Ah\ 2 15 

lead with the oil of vitriol than without it. 
He mentions, p. 28, his procuring 36 cu- 
bic inches of air from 48 dwts. of red lead. 
But from 2 ounces, or 40 dwts. of fuch 
red lead as I now ufe, I a^i able to g^t, 
by heat only^ 24 ounce meafures of air, 
which is almofl 48 cubic inches. Mixing 
half the weight of oil of vitriol with this 
red lead, I got as nearly as poiTible, the very 
fame quantity of air; and when I mixed 
oil of vitriol with red lead out of which 
I had by calcination expelled all its air, it 
yielded nothing but a very fmall quantity 
of fixed air. 

It was not till after I had made the ex- 
periments before recited on manganefe, 
and other mineral fubftances, that I thought 
of fubjed:ing j^r^^;^ 'uitriol, and other faline 
matters, to the fame triaL It is true I had 
tried therji before -, but the method was not 
adequate to the purpofe. And though I 
had even got a fmall quantity of air con- 
fiderably better than common air from 
'Roman vitriol (See vol. II. p. 86.) I had 
concluded that " there muft certainly 

Pa ** have 

2. 1 6 Obfervafions on 

*' have been fome nitrous acid in that 
*' Roman vitriol." In this cafe, there- 
fore, as in the experiments with, fait petre, 
and alum, I had made a difcovery without 
being fenfible of the value of it, or indeed 
underflanding it. Nor, when I refumed 
my experiments on vitriol, had I any ex- 
pectation of getting from it any thing befides 
fixed air and water. However, having every 
thing at hand, a very flight motive was fuf- 
ficient to induce me to include this among 
other articles deftined for the fame procefs. 
In this manner, therefore, without ex- 
pecting the actual refult, on the 24th of 
November 1777, I put an ounce of green 
vitriol into a glafs veffel, and with a fand 
heat got from it, at firfl, after the common 
air was expelled, and the vapour of the 
water combined with it was come over, a lit- 
tle fixed air j then, after fome interval, a large 
quantity of vitriolic acid air ; the refiduum 
of which was at firft hardly perceivable, 
but was afterwards confiderable, and chiefly 
fixed air. When the refiduum was ftill 
more confiderable, I found that it was 


Dephlogifticated Air* 2 1 ^ 

diminished by nitrous air, at length it had 
no mixture of vitriolic acid air, but was 
very turbid, and appeared to be pure de- 
phlogifticated air, except that, at the laft, it 
was not quite fo pure as before, which I 
thought rather extraordinary. Of this de- 
phlogifticated air, I colledled ten ounce mea- 
fures. What remained in the glafs veftel 
was 6 dw. of a purplifh coloured ochre. 

On this refiduum I poured a quantity of 
fpirit of nitre, which mixed with it as it 
does with clay, without any fenlible heat; 
and then it yielded two ounce meafures of 
air, the greateft part of which "was fixed air, 
and the remainder dephlogifticated, except 
If , a little at the laft, which, contrary to what 
happens in moft other proceftes, was phlo- 
gifticated, not being at all diminiftied by 
nitrous air. Probably, however, there may 
be a 'quantity of phlogifton fo intimately 
combined with this ochre (and its deep 
colour makes this not improbable) that 
nothing but a great degree of heat can 
expel it; when it will, of courfe, vitiate 
the air that is generated at the fame time. 


21 8 Obfervations on 

Notwithftanding this evident produdlion 
of a confiderable quantity of dephlogifti- 
cated air from green vitriol, which is a 
combination of iron and the vitriolic acid, 
I ilill fufpedted, as in the cafe of the Roman 
vitriol mentioned before, that, by expofure 
to the common atmofphere, or in fome 
other unknow^n manner, this vitriol, which 
had been bought at a common fhop, might 
have got fome mixture of fpirit of nitre. 
I therefore made a quantity of vitriol 
myfelf by diflblving iron filings in oil 
of vitriol, diluted with water. This 
vitriol, treated as the former had been, 
yielded air of all the fame kinds, and in 
the fame proportions, as in the preceding 
experiment ; the dephlogiilicated air, as 
then, being very turbid, and exceedingly 
pure. The firft air that came over was the 
common air in the vefTel a little phlogifti- 
cated. A very fmall quantity of fixed air 
was ftill obferved in the reiiduum of the 
vitriolic acid air, but none after the de- 
phlogifticated air was procured. 


Dephlogifiicated Air. 219 

It now, however, occurred to me, that as 
nitre is ufedin the comrnon procefs for making 
oil of vitriol in large quantities, there might 
be a mixture of this, and in all th^e oil of 
vitriol of the common fort, I therefore, 
in the next place, made ufe of Newman's 
oil of vitriol, which I was informed was 
made in the old method, in which no 
nitre is ufed. With this I made fome 
green vitriol as before ; and, diftilling it to 
drynefs with a fand heat in a glafs n^^^^^j 
I got from it firft a conliderable quantity of 
phlogifticated air, then pure fixed air, but 
not much ; and, laftly, neglecting the 
vitriolic acid air, pure dephlogiflicated air, 
though in a fmaller quantity than before. 
But this I impute to my not having care- 
fully feparated the vitriol that I had made 
from the iron filings that remained un- 
diffolved in the diluted oil of vitriol. For 
the whole mafs that I made ufe of was of 
a dark colour, containing much iron, mixed 
with the cryflals of the vitriol. 

In making the vitriol for all the above- 
mentioned experiments, I had taken care 


2t20 Obfervations on 

that the cryilals fhould be formed at the 
bottom of a deep glafs velTel, fo as to have 
no vifible communication with the external 
air; and I had alfo covered the veflel as 
carefully as I could during the procefs, and 
had fpent as little time as poffible in con- 
veying the vitriol from the vefTel in v^hich 
it v^as formed into that in which it was to 
be diflilled. I determined, however, to 
avoid the fmall objedion to which this 
trifling expofure to the air was liable, and 
therefore next made the diflillation in the 
fame retort in which the folution had been 
made, and in the continuation of the fame 
procefs, fo that all communication with 
the external air was moft efFed:ually pre- 

For this purpofe I diifolved 6 dw. 4 gr. 
of iron in diluted Newman's oil of vitriol, 
and diitilling to drynefs in a retort with a 
long neck, I got from it, after the com- 
mon air was expelled, a fmall quantity of 
fixed air, a prodigious quantity of vitriolic 
acid air, and likewife about 22 ounce 
meafures of the pureft dephlogifticated air. 


T)ephlogijilcated Air. 2.21 

With more heat, I believe more of this air 
might have been procured. The common 
air that came over at this time was not at 
all phlogifticated. When I examined the re- 
liduum, I found remaining i dw. 15 gr, 
of iron undilTolved, fo that the 22 oz, 
meafures of dephlogifticated air had been 
yielded by 4 dw. 13 grs. of iron. 

Being informed by fome of my chemical 
friends, that, probably, there is more or 
lefs of fpirit of nitre in all oil of vitriol, 
when it is firft made, and that even diflilla- 
tion cannot be abfolutely depended upon 
for a perfect feparation of it, I delired Mr. 
Winch to prepare me a quantity of oil of 
vitriol in fuch a manner, as that he could 
engage for its containing no fjpirit of nitre 
whatever, and with this I was determined 
to make my laft experiment, and acquiefce 
in the refult, whatever it fhould be. 

Accordingly Mr. Winch having furnifh- 
ed me with this oil of vitriol, I difTolved 
in it 6 dws. of very clean iron, and diflil- 
ling it to drynefs, in a long necked retort, 
I received the common air a little phlogifti- 

22^ Obfertafions dfi 

cated, a little fixed air, much vitriolic aclcJ 
air, and laftly i8 ounce meafures of de- 
phlogifticated air. The iron that remained 
undilTolved weighed 23 grs. fo that the air 
was yielded by 5 dwts. i gr. of iron* 
The nitre weighed 7 dwts* 13 grs* fo that 
there probably remained a quantity of oil of 
vitriol in the nitre, and confequently, had 
the heat been greater, more air might hav^ 
been procured. 

To try what might be done with a gun 
barrel, which could bear more heat than 
the glafs retort, I put the refiduum of the 
above-mentioned experiment, and alfo of 
that in which I had ufed 6 dwts. 4 grs. of 
iron together; and after they had been 
expofed to the common air all night, I put 
them into the gun barrel. But, with as 
much heat as I could give to it in a charcoal 
fire, with a pair of bellows, I only got 
from it about an ounce meafure of air, half 
of which was fixed air, and the refl phlo- 
gifticated. The ochre from the gun-barrel 
was black. I fufpe(5t, however, that, could 
I have gi^en thefe materials the fame degree 


^ T)ephlogiJitcated Air, 223 

of heat in an earthen retort, the air would 
have been both purer, and more in quantity. 

Being now fufficiently fatisfied that pure 
oil of vitriol would always yield dephlogif- 
ticated air with iron, it only remained to 
try whether the ochre remaining from the 
former experiment, from which air had 
been procured, would yield more air with 
more oil of vitriol, which is the cafe with 
red lead and fpirit of nitre. 

Accordingly, I put more oil of vitriol to 
this refiduum (obferving that it became 
very hot by this mixture, as red lead does 
with fpirit of nitre) and then, with a red 
heat, in a glafs retort, it yielded a quantity 
of vitriolic acid air, no fixed air, but 24 
ounce meafures of dephlogiflicated air 5 
when, the retort being melted, a good deal 
of the air was neceffarily loft ; for the pro- 
duce of air had not begun to flacken when 
this accident happened, and removing the 
retort from the fire, I found only about 
half of the matter turned red, while the 
remainder was white. From this circum- 
ilance I concluded, that before I had net 
'■ 2 got 

224 Obfervations on 

got more than half the air that it would 
have yielded. Refuming the procefs in a 
gun-barrel, I adtually got about as much 
air as I had done before. 

I had not now the leaft doubt remaining 
but that the acid of vitriol, at leafl with 
iron, is capable of properly generating de- 
phlogifticated air, as well as the acid of 
nitre with lead, or any other fubftance 
whatever. All this trouble I was led to 
take in confequence of entertaining an 
unreafonable doubt with relpedt to the ex- 
periment made with the Roman vitriol, of 
which an account is publifhed in my fecond 
volume 3 and, indeed, for want of reflediing 
properly on that made with alunii of which 
an account may be i^txi in my firft volume. 

To complete my experiments on the 
vitriolic acid and iron, I took half an ounce 
of the common ruft of iron, fuch as is ufed 
by apothecaries ; and pouring upon it a 
quantity of that acid, obferved that it im- 
bibed it very eagerly, and became of a dark 
and almoft a black colour. Then ufing a 
gun-barrel, I got from it two pr three pints 


JDephlogiftkated Air. 225 

of air, all of which was fixed air, but with 
a large reliduum, about a third of the 
whole, phlogiftitated aire 

As the Gommon ruft of iron contains a 
good deal of phlogifton, 1 did not expedt 
any better refult from this experiment. 
But having, in fome meafure, purified it 
by this procefs, I put more oil of vitriol 
to what remained of the ruft of iron, and 
then I got from it only a little fixed air, 
and fixteen ounce meafures of dephlogifti- 
cated air. 

It is evident both from thefe experi- 
ments with the vitriolic acid, and thofe 
cited ia my fecond volume with fpirit of 
nitre, that the earth oi iron is eafily con* 
verted into air -, provided (which I think 
the moft probabk) that any earth enters into 
the compofition of air. Should it be of 
this kind of earth that the bulk of atmo- 
fpherical air in fad coniifts, it may perhaps 
help to account for the magnetifm of Hhe 
whole globe of the earth. This hint was 
fuggefted to me by Mr. MichelL 

Q^ SEC- 

226 Ohfervatmis on 


Of the ProduBion of Deplogijiicated Air 
by Means of the Vitriolic Acid, from other 

'AVING got all indifpii table protluc-»- 
tion of pure air from iro72, by means 
of the vitriolic acid, it was natural for me 
to proceed to iimilar experiments on other 
metals, with the fame acid. And, in the 
firft place, I made the proper trials with 
the two remaining kinds of vitriol, the 
blue, into which copper enters, ahd the 
white, which is compofed of zinc ; and 
having now no doubt remaining with re- 
fpedt to the purity of the vitriolic acid 
which enters into the compoiition of thefe 
kinds of vitriol, I contented myfelf with 
fpecimens bought at the fhops, and did 
not think it neceifary to take the trouble to 
cotnpofe them myfelf. 

In my firil trial with an ounce of blue 
vitriol I got no air at all,, neither vitriolic 


Dephlogijikated Air. 22J 

iacid air^ fixed air, nor dephlogiftlcated air. 
This want of fuccefs, I imagine, was owing 
to my not being able to apply fufficient 
heat, in the manner in which I then made 
the experiment. For I fucceeded better 
another time, when from about half an 
ounce of blue vitriol, in a glafs velTel, I got 
a little fixed air, and one ounce meafure of 
dephlogiilicated air. The vefifel breaking, 
I put the materials; into a gun-barrel, and 
then gQt from them about 25 ounce mea- 
fures of dephlogifticated air, with hardly 
iny more fixed air. The greatell part of 
this air was very turbid. 

In the next place, I diflblved copper in 
oil of vitriol; and having put half an ounce 
of copper to a quantity of oil of vitriol, in 
a glafs retort, and diftilled it to drynefs, I 
got, befides vitriolic acid air, a quantity 
pf fixed air, and an ounce meafure of de- 
phlogifticated air; when the glafs was 
melted, and fome air efcaped. Breaking 
the hard mafs within the retort, when it 
was cold, the outiide was of a browniHi 
0^2 colour, 

228 Olfervatkm on 

colour, inclining to yellow, and the infide 


Taking thefe materials from the retort, 
I put them into a gun-barrel ; and, with 
as rtiuch heat as I could apply in a charcoal 
fire, with a pair of bellows, I got from them 
befidcs fixed air, of which there might 
be an ounce meafure in all, ten ounce mea- 
fures of dephlogifticated air. I found 
that not more than half the copper was 
diiTolved : for though there was vitriolic 
acid enough for the purpofe, yet the pieces 
of copper not being very thin, a cruft had 
heen formed on the outfide of them, that 
defended them from the farther adion of 
the acid, even in a boiling heat ', ivt that I 
concluded that, had the copper been com- 
pletely difiblved, and the procefs managed 
in the befi: manner about 30 ounce meafures 
of dephlogifticated air might have beea 

To finifh my experiments on the three 
vitriols, I took an ounce of calcined white 
vitriol, and, v/ith a gun- barrel, I got from 


Depblogijiicated Air, 229 

it a great quantity of vitriolic acid air, fome 
fixed air, with, five ounce meafures of de- 
phlogifticated air. At another time, from 
one ounce of this kind of vitriol, but 
uncalcined, I got only about two ounce 
meafures of air, part of which was fixed 
air, and part dephlogifticated airj not 
reckoning a great quantity of vitriolic acid 
air, which came, as ufual, before the de- 
phlogiflicajted air. 

To proceed with xind as I had done 
,with the iron and copper, I put a quantity 
of oil of vitriol to half-an ounce of Jlowers 
of zinc ', and, in a gun-barrel, got from it* 
three ounce meafures of air, a fmall part of 
which was fixed air, and the reft nearly as 
good as common air. Had I made ufe of a 
glafs velTel, I make no doubt but that I 
fiiould have got much more air, and much 
purer. For whatever it be in a procefs that 
injures air, it lelTens the quantity of it. 
Three or four time? the quantity of pure, 
or dephlogifticated air, muft be ufed to 
make a given quantity of common air, and 
CL3 ftill 

^^o Obfervations on 

Hill more is requifite to make the fame 
quantity of phlogillicated air. 
■ I did not think it of much confequencc 
to my purpofe to go through all the metals 
with this procefs, and therefore only made a 
trial of fuch as I happened to have at hand. 

With Jilver I had no fuccefs -, owing, 
perhaps, to " its requiring more heat than I 
could apply in a glafs velTel. I made the 
folution in a flint glafs retort, and this 
happening to break when it was evaporating 
to drynefs, I removed the mafs^ which was 
yellow, into a green glafs retort 5 and, 
melting it, I got from it about an ounce 
meafure of fixed air, which might poffibly 
come from its being a little tinie expofed to 
the common air, in transferring it from 
one retort to the other. But after this I 
got no more air of any kind, though the 
mafs continued liquid, and even red hot at 
the bottom of the retort a confiderable 
time; and at length the retort, unable to 
fuftain any more heat, melted. 

Turbith mineral, which is made by a 
^lution of quickfilver in oil of vitriol was 


"Dephlogifikated Air , 231 

on6 of the fubftances from which Mr. 
Liindriani procvired dephlogifticated air ; 
though, for the reafon mentioned above, I 
had not profited by his obfervation. But 
mereury being always at hand for the pur- 
pofe of my experiments, I made trial of it, 
as of other metals in this courfe ; and 
though I did not afcertain the exad: quan- 
tity of dephlogiflicated air that may be 
procured from a given quantity of mercury 
by this means, I, however, fully fatisfied 
myfelf, that a very great quantity may be 
procured from it, and the procefs itfelf is 
a peculiarly pleaiing one. 

I dilTolved an ounce of quickfilver, puri- 
fied by agitation in water, in pure vitriolic 
acid, in a green glafs retort. During the 
diftillation to drynefs the retort broke 1 but 
collecting the materials as well as I could 
(in which perhaps one-tenth of the whole 
might be loft) I put them into a frefh retort, 
and, expofing them to a red heat, got from 
them a great quantity of vitriolic acid air, a 
good deal of fixed air, and about fifty ounce 
nieafures of dephlogiflicated air, 

0^4 During 

Sjs Obfervattons on 

During the procefs the folution boiled 
violently in the form of a red liquor, while 
the upper part of the retort was coated with 
a whitiih fort of matter. As the heat 
reached this coating, it alfo became red| 
and during the whole procefs that which 
evaoorated was collected on the fides of the 
retort, and then defceded to the bottom, like 
drops of blood, or red ink, fo as to make 
a very pleafing appearance. After the pro- 
cefs, a very little reddifh matter remained 
at the bottom and on the fides of the retort, 
which, as well as that which was collected 
at the neck of the retort, became white 
when it was cold. Very little of the 
quicklilver was revivified. 

That I might form the better judgment 
of the quantity of air that might be ex- 
trad:ed from an ounce of quicklilyer, I 
collected, as well as I could, all the matter 
that adhered to the neck of the retort, and 
expofmg it to the heat a fecond time, I got 
ten ounce meafurcs of air more, with the 
fame phenomena as before.* Still, however, 
much of the matter adhered to the neck of 


Dephlogifttcated Air. 233 

the retort ', fo' that how much air might 
have been procured, if the moll had been 
made of the folution, I cannot tell with 

As the breaking of the retort in the micl- 

dle of the former procefs (in confequence 

of which the materials were expofed to the 

common air, and cooled in it) might leave 

fome fufpicion that the dephlogifticated air 

procured had been imbibed from the atmo- 

fphere, I repeated the procefs with a view 

to that circumilance. DilTolvingan ounce 

of pure mercury in two ounces of pure oil 

of vitriol (frequently diftilled) in a fmall 

retort with a long neck, the end of which 

was always immerfed in quickfilver, or 

water; after the vitriolic acid air came 

over, which made lime water turbid (owing 

probably to a mixture of iixed air) I received 

twenty ounce meafures of dephlogifticated 

air; when, the retort melting with the 

heat put an end to the procefs. My pur- 

pofe, however, was fufficiently anfwered, 

as I had fully afcertained the production of 

dephlogifticated, if not of fixed air alfo, 


2^4 Obfervatlonsjin 

from thefe materials, without the help of 
any thing that might have been communi- 
cated to them from the atmofphere. When 
I come to treat of fixed air, I Ihall produce 
fufficient proof of the generation of fixed 
air from the acid of vitriol ; as in my former 
publication, I fhewed that it was fome- 
times indifputably generated from fpirit of 
nitre ', fo that I then concluded that it was 
a modification of that acid. 

It is remarkable that, either by means 
of oil of vitriol, or fpirit of nitre, quick*- 
filver yields a very great quantity of dephlo- 
giflicated air 5 but with this difi^erence, 
that in the procefs with fpirit of nitre, 
almofi: the whole of it (that is, if the pro- 
cefs be conducted with care, with the lofs 
of not more than the twentieth part of the 
mercury) is revivified, and therefore may 
be ufed again and again ; whereas, in the 
procefs with the oil of vitriol almofi: all the 
mercury is loft. 

The only metalic fubftance that I could 
conveniently make a trial of after- this was 
Xaxv'^ but the procefs being made in a gun- 

Depblogtfticated Air, 12,^^. 

barrel, it yielded no dephlogifticated air at 
all. For this purpofe I moillened an ounce 
of putty (which I was affured was not of the 
common fort, but a pure cal?: of tin) with 
oil of vitriol, and I got a little fixed air, 
and two or three ounce meafures pf phlo- 
gifticated air. It is very probable that the 
phlogifton might come from the gun-barrel, 
and, by injuring the air, might make it 
yield a fmall quantity of phlogifticated, in- 
ftead of a large quantity of dephlogifticated 
air. What this procefs would have yielded 
in a glafs veflel I cannot tell. 

5 E C^ 

2^6 Ohfervatims dn 


Of the ProduSlton of Dephkgijiicated Air 
from Earthy Substances by Means of 
the Vitriolic Acid* 

Y obfervations on the fubjeft of this 
fedlion have not been many, but 
they are fufficient to fatisfy me that pure 
air may be procured by the acid of vitriol 
from earthy fubjiances that are not of a 
metalic nature -, though, as was the cafe 
with the acid of nitre, not, in general, in 
fo great abundance as from the metalic 
earths. But what might be the refult of 
trials on a greater number of earthy fub- 
flances I cannot pretend to fay. 

One of the jfiril fubftances from which I 
extracted pure air, as I obferved before, 
was alunti that is the earth of alum united 
to the acid of vitriol. But having over- 
looked that experiment, and not having 
got any good air from alum in my procefs 
with a burning lens in mercury (though 


Dephlogiftkated Air. t^y 

indeed the quantity was too fmall for the 
purpofe) it did not occur to me to make 
any farther trial of it, till I was engaged 
in the prefent courfe of experiments. I 
was now, however, fully fatisfied, that 
dephlogifticated air may be procured from 
it, though probably in no great quantity. 

When I had well calcined a quantity of 
alijm, I put it into a glafs veflel, and with 
a red heat I got from it a little fixed air, 
and fome that was clearly dephlogifticated ^ 
but an accident interrupting the experi- 
ment, I could not judge of the quantity 
that might have been procured. At ano- 
ther time, I got a pretty large quantity of 
air from calcined alum, all that it could be 
made to yield in a common fire, urged 
with a pair of bellows. The bulk of it was 
phlogifticated air, with about half hx^d, 
air, the laft produce not being quite fo 
good as common air, though it was nearly 
fo. Part of the ^lum had a tinge of black, 
acquired from the fm oke of the fire in which 
the calcination was made ; and this circum- 
ftance tnight contribute to deprave the air. 

-2 h2SkU, 

^^S Obfervatiojis on • 

Laftly, from an ounce of calcined alum^ 
prepared fome nionths before, I got about 
iix ounce meafures of- ^ir, all quite as 
good, or better than common air, and 
without any fixed air in it. The procefs 
was in a gun-barrel, and the refiduum of 
the alum was very hard. This I moiftened 
with oil 6f vitriol, ftill keeping it hard 
and dry ; and, iii a gim-barrel, it yielded 
again two or three ounce meafures of air," 
chiefly fixed air, and at lafi: fome that was 
about as good as common air. After thi^ 
it was remarkable that this matter abforbed 
air, perhaps about an ounce meafure in all. 
This I obferved twice, arid it may be worth 
while to inveftigate this circumftance a 
little farther. 

To half an ounce of quick lime, I put 
Oil of vitriol till it weighed i oz. 4 dwts. 
when It made a hard mafs. This I pounded, 
and putting it into a gun-barrel -, I got 
from it, in all, about ten oiince meafures of 
air, the greateft part of which was fixed 
air^ but towards the laft, when the heat 
wa§ as great as I could make it, in a 


Dephkgijiicated Air. 235 

common fire, urged with a pair of bellows, 
the reliduum was as good as common air^ 
or rather better. This air came over very 

Manganefe yielding dephlogifticated air 
without the help of any acid, it might be 
thought more proper for the produftion of 
air with that affiftance, as ftiinium is with 
refpe6t to the nitrous acid. I therefore 
tried it on the 15th of April, when to one 
ounce of this fubftance, which had beerfc 
kept red hot a long time on the loth of 
November preceeding^ I. put fome oil of 
vitriolj which it imbibed eagerly 5 and 
then got from it about twelve ounce mea- 
fures of air^ the whole of which was fixed 
air, except about one ounce mcafure, which 
was about as good as common air. In this 
experiment I believe I made ufe of a gun 
barrel, fo that probably more, and better 
air would have been procured in a glafs 

S E C- 

$4^ Ohfervatwht on 


Attempts to procure Air from various Suh^ 
Jiances by means of Spirit of Salt ^ 

R. Landriani had informed me that 
he had got dephlogifticated air 
from corrqfive Jhblimate, as well as from 
turbith mineral. But trying this, in the 
b'^d manner I could, immediately upon the 
receipt of his letter, I was not able to pro- 
cure any air from it; and though I have 
varied the procefs, I am ilill unable to pro- 
cure any. It was this failure (from what 
caufe I cannot tell) that prevented my 
proceeding to the turbith mineral at that 
time, as has been mentioned before. 

I firft put a quantity of corroiive fubli- 
mate into a tall glafs veffel, then filling it 
up with quickfilver, I inverted it in a bafon 
of the fame, and expofed the fublimate to 
as much hoat as the glafs would bear, in 
the manner defcribed in the Introdudion. 
The glafs was even melted ^ but when all 


Dephlogijiicated Air. 241 

was cool, it appeared that no air had been 
produced. . The mercury rofe and filled 
all the interftices of the fublimate. 1 then 
put two ounces of this fubftance into a 
green glafs retort, which will bear a greater 
degree of heat than flint glafs ; and by de- 
grees covered it with live coals, but all that 
followed was the fublimation of the matter 
into the neck of the retort, and no pro- 
dudtion of air. Even the common air, that 
came over firft, was not at all altered. 

I was not able to make much more of 
common fait. From an ounce of it, in as 
llrong a red heat as I could give it in a glafs 
retort with a long neck, and in fand (in 
which it may be made to bear more heat 
than when furrounded with live coals) I 
got about two ounce meafures of air, the 
firft part of which was fixed air, and the 
laft phlogifticated air, extinguifhing a 
candle, and not affedled by nitrous air. I 
have, however, at various times, repeated 
this experiment, and once with the heat of 
a fmiths fire -, but getting little or no air, I 
rather fufped that the phlogifticated air in 
R the 

24'2 Obfervattons on 

the preceeding experiment came from fome 
particles of foreign matter, that, un- 
perceived by me, might be mixed with 
the fait, rather than from the fait itfelf. 

As iron is ealily foluble in fpirit of fait, 
and yields abundance of inflammable air, 
I was in hopes that this folution, diftilled 
to drynefs, might yield dephlogifticated, 
or fome other kind of air 5 and with this 
view I diflblved half an ounce of iron in 
fpirit of fait, and diftilled it to drynefs in 
a green glafs retort. But I got only a very 
fmall quantity of fixed air, jufi: fufficient 
to precipitate lime in a velfel of lime water, 
in which the air was immediately received, 
and yet the whole mafs wa^ kept perfedly 
fluid with heat. 

In dilTolving this iron in fpirit of fait, 
I obferved that when the large bubbles 
burft, they were full of a whitifh matter, 
refembling the cloudy appearance of nitrous 
air when it is produced very rapidly. It 
feems, therefore, that all the kinds of air, 
by whatever acids they are procured, con- 
tain earth, either in a diflblved flate, or as 

a con- 

Dephlogifticated Air. 24^ 

a conflituent principle in their compofltion. 
For when much heat is tifed in the pro- 
dud:ion of any kind of air, it contains 
more earth than it can hold when it is re- 
duced to the temperature of the atmof- 

To make a final experiment of this kind 
upon iron, which yields air with peculiar 
readinefs in moft other procefTes, I diiTolved 
3 dw. 8 gr. in diftilled water impregnated 
with marine acid air -, but, diftilling it 
to drynefs in a long necked retort, and ap- 
plying as much heat as the glafs would bear, 
I got nothing but a very fmall quantity of 
£xed air, the refiduum of which was phlo- 

The lafl trial I made of this acid was 
with quick lime, which is diffolved with 
great rapidity, and in great abundance by 
fpirit of fait. Half an ounce of it I fatu- 
rated with fpirit of fait, and putting it 
into a green glafs retort^ I got no air at all 
from it, even in red heat ^ but the laft 
portion of the common air that came over 
w'as- phlogiflicated. I then put it into a 

244 Obfervatlons on 

gun barrel, and with as much heat as I 
could give it in a common fire, urged with 
a pair of bellows, I got from it about 
twenty ^vz ounce meafures of air, part of 
which was fixed air, and the reft inflam- 
mable, burning with a blue flame. This, I 
have little doubt, came from the iron 3 and 
the mixture of fixed air from the lime 
would make it burn blue. When the 
production of this air was pretty quick, it 
was turbid, as in other cafes. 

Upon the whole, I think I may conclude 
from the experiments recited in this fed:ion, 
that the marine acid difiers efl!entially from 
both the vitriolic and nitrous in this, that it 
cannot, hj any combination whatever, bq 
made to yield dephlogifticated air, at leaft 
with the degree of heat that I was able to 

S E C- 

Dephlogtjiicated Air, 245 


Mifcelianeous Experiments relating to De^ 
phogijiicated Air, 

I. lihe very great diminution of Dephlo" 
gijiicafed Air by Nitrous Air. 

IT appears from my firft obfervations on 
the properties of deplogiilicated air, 
that, in general, when two equal meafures 
of nitrous air are mixed with one meafure 
of it, the whole is reduced to half a meafure, 
and fometimes, when I thought it pecu- 
liarly pure, to one fixth of a meafure. I 
have fince, on one particular occafion, pro- 
duced this kind of air in a flate of fo 
much greater purity as appeared very extra- 
ordinary to myfelf, and I doubt not will 
be thought fo by others. 

Having, for a purpofe that will be men- 
tioned in the account of my obfervations 
on fixed air, kept a folution of mercury in 
fpirit of nitre for feveral months, in a 
phial with a ground ftopper, I put it into 
a retort with a long neck, and, in a fand 
R 3 heatj 

24^ . Obfervatlons on 

heat, received in the firfl place, the nitrous 
air it yielded, and then without removing 
the retort from the fire, the dephlogiilicated 
air. Ufmg both the nitrous and dephlo- 
giilicated air of the fame produce, I ob- 
ferved that two meafures of the former and 
one of the latter mixed together, occupied,- 
after the effervefcence was over, the fpace of 
no more than three hundred parts of a mea- 

It was impoffible for me to be millaken 
with refpeit to this remarkable fad; for 
the tube in which I meafured the reliduum 
was fo long, in proportion to the capacity 
of the phial which I ufed as a meafure, 
that a hundredth part of a meafure exceed- 
ed the eighth of an inch. Repeating the 
experiment, I found that two meafures of 
nitrous air were rather more than fufficient 
to faturate one meafure of the dephlo- 
giilicated air; {o that, poiHbly, had the 
former experiment been made with more 
circumfpeftion, the diminution, extraordi- 
nary as it was, would have been fomewhat 
greater. Indeed it cannot be fuppofed, that 


t)ephlogiJiicated Air, 247 

ixaBly two meafures of nitrous air fhould 
be the precife quantity that would produce 
the greateft diminution. It fhould alfo be 
confidered, that a fmall portion of air might 
be yielded by the water in which the ex- 
perin.ent was made. 

Upon the whole, therefore, I am inclined 
to think that, were it poffible to make both 
the nitrous and dephlogifticated air in the 
greateft purity, and then to mix them- in 
fome exadt proportion, the aerial form of 
them both would be entirely defliroyed, 
the whole quantity feeming to difappear, as 
in the mixture of alkaline and acid air. 
But whereas a white faline fubftance is the 
immediate viiible refult of this mixture, 
there is no vifible produce from the other, 
the whole, whatever it be, being diffolved 
in the water; fo that, this would probably 
be the more flriking phenomenon of the 
two ; and the mixture of acid and alkaline 
air never fails to excite a good deal of 
aftonifhment, efpecially when they arp 
previoully made, and contained in feparate 
yelTels, and then fuddenly mixed together, 
R 4 by 

248 Obfervaftons on i 

by transferring them from one veflel to 

another in a trough of quicklilver. 

Willing to get dephlogifticated air in a 
ftate of the greateft purity, and having ob- 
ferved that it fometimes comes over mixed 
with the red vapour of fpirit of nitix, fome 
times quite tranfparent, and again exceed- 
ingly turbid with the white matter, de- 
pofited in the cold recipient; I thought 
that, poffibly, it might differ in purity ac- 
cording as it was procured in thefe different 
circumftances. To try this, I diffolved a 
quantity of mercury in fpirit of nitre, and 
putting the folution into a long necked re- 
tort, I diftilled the whole to drynefs; 
then, placing the retort in a fand heat, I re- 
ceived all the air that came from it in 
feveral portions, iiril that which was mixed 
with the red vapour, then that which came 
while the tube was quite tranfparent, then 
that which was very cloudy with the 
whitilh matter, and laffly that which came 
after it was tranfparent again -, but I did 
not find that there was any feniible dif- 
ference between any of thefe portions of 


Dephlogifikated Air, 249 

dephlogifticated air. They were all equally 
pure. The red vapour certainly tends 
to injure the air, but I fuppofe more time 
was requilite to produce a fenfible efFedt 
than this procefs admitted. 

2. Of procuring dephlogijiicated Air by means 
of crude Nitre. 

It is much to be wifhed, that fome me- 
thod could be found of making dephlo- 
gifticated air in great quantities, and very 
cheap ', and I am not without hopes, that, 
in time, much cheaper procelTes will be 
hit upon than thofe that are now in ufe for 
fe that purpofe. At the time of my laft pub- 
lication I generally made ufe oi fpirit of 
nitre, which is a dear article in chemiftry. 
At the fame time I had alfo procured air from 
nitre itfelf, though only in an inconfider- 
able quantity. Mr. Scheele, however, I 
find, generally makes ufe of nitre only for 
whatever quantity of this kind of air he 
makes ufe of ^ and I had been informed 
that fome perfons had procured great quan- 
tities of this air from a mixture oifand and 


250 Ohfer'oatlons oii 

nitre. This I imagined to be occafioned by 
the acid of the nitre being gradually dif- 
. engaged by the heat, and uniting withfuch 
earthy matter as was at hand to combine 
with it in this new manner. More air 
might be procured by this means, becaufe, 
when the fpirit of nitre previoufly formed 
is made ufe of, far the greater part of it is 
thrown off by the heat of the procefs, and 
never contributes to the formation of air 
at all. 

I therefore made a few trials of a mixture 
of nitre and various kinds of earth, and 
found that, in feveral cafes,- more of the 
air would be procured by means of crude 
nitre than by the nitrous acidj fo that a 
confiderable faving would, no doubt, be 
made by this means. But then I found 
that much more heat was neceffary for the 
purpofe, fo that the expence of fuel would 
be more confiderable. I am fatisfied that 
it is by means of much greater heat than I 
have ever applied that Mr. Scheele gets fo 
large a quantity of dephlogiflicated air from 
nitre only; and the celebrated Mr. Pott ot 
r Berlin> 

Dephlogifticafed Air. 251 

Berlin, I am informed, has expelled all the 
acid of nitre by mere heat, leaving nothing 
but its alkaline bafe. Had the elaftic 
matter which he expelled been colleded,. 
it would, no doubt, have been dephlo- 
giilicated air ; and it would be curious to 
afcertain the quantity of this air from a 
given weight of nitre. As to myfelf, I have 
never had the ufe of a regular laboratory, 
and hitherto have never applied more heat 
than I could raife in a common fire, urged 
with a pair of bellows ; except that, on 
particular occafions, I have had recourfe to 
a fmith's fire. 

In company with Mr. Magellan, I endea- 
voured to procure dephlogifticated air from 
nitre and common fand ; but for want, I 
fuppofe, of fufficient heat, the quantity we 
got was inconfiderable 5 and he has fince 
informed me, that the fand is not at all 
neceffary, but only a greater degree of heat 
to be applied to the nitre. I found, how- 
ever, that, with the fame degree of heat, I 
could get more air from a mixture of nitre 
and various other fubflances, than I could 


252 Ohfervattons on 

from the nitre alone ; though I got more 
air by means of nitre than of fpirit of 
nitre, as I obferved above. The experi- 
ments I made were as follows. 

From lefs than half an ounce meafure of 
pounded fait petre, and the fame quantity 
of fait of tartar y well mixed together, I 
got, in a glafs veffel, with a red heat, 17 
ounce meafures of dephlogifticated air, be- 
iides about a fourth part of fixed air mixed 
with it, in all the ftages of the procefs ; 
whereas from a whole ounce meafure of 
fait petre, treated in the fame manner, 
without any mixture of fait of tartar, I got 
only 1 3 ounce meafures of dephlogifticated 
air, befides a fmall quantity of fuch air as 
made lime water a little turbid. 

To try the difference between nitre and ' 
fpirit of nitre, I made ufe of the flowers of 
zinc. Half an ounce of thefe mixed with 
a quarter of an ounce of fait petre, in a 
glafs v^Qtly and a red fand heat, yielded 
22 ounce meafures of dephlogifticated air; 
but the whole procefs took up no lefs thart 
three hours. The air often came very 


'Dephlogljlicated Air, sr-a 

irregularly, though fometimes pretty equa- 
bly. The remainder of the materials 
weighed conliderably lefs than the flowers 
of zinc. From the fame quantity of the 
flowers of zinc and a quarter of an ounce 
of ftrong fpirit of nitre, I got not more 
than 1 1 ounce meafures of dephlogifticated 
air, or half the quantity that I got before ; 
the tubes through v/hich it was conveyed 
being filled with red fumes, by which much 
of the fpirit of nitre mufl neceiTarily have 
been loft. 

3. Of the rujling of Metals in Air, 
It is generally thought, I believe, that 
metals expofed to the open air are corroded, 
and contradt ruft, by means of fome acid 
vapour contained in it. I thought it poffi- 
ble, however, that very pure air might 
have fuch an affinity with phlogifton, as to 
deprive fome metals of it, without the aid 
of any acid. To try this, I filled an eight 
ounce phial with very dry clean nails, and 
then with quickfilver, which I difpkccd 
by very pure and dry dephlogiflicated air, 


254 Ohfervattons on 

and left it inverted- in a bafon of quickfilver 
on the 13th of April 1778. At this time, 
.*uiz. the 26th of January 1779, I find that 
one tenth of the whole quantity of air is 
gone, the quickfilver having rifen fo high 
in the phial. I therefore take it for granted, 
though I cannot perceive any ruft on the 
nails, that my conjecture is wtW founded ', 
that the air has been diminifhed by means 
of phlogifton from the iron, and that in 
time, if the quantity (hould be fufficient, 
the rufl will be apparent. 

4. Of the Detonation of Nitre, 

The difcovery of dephlogifticated air 
throws great light on many very important 
fadts in chemiftry, but upon none more 
than upon that very difficult and ftriking 
one of the detonation of nitre, concerning 
which the moll improbable conjediures 
have been advanced by the moll eminent 
philofophers and chemifts. This detona- 
tion is the fudden inflammation produced 
by the conta<5l of various fubllances con- 
taining phlogillon and nitre, when either 


'Dephlogifiicated Air, z^t 

of them is red hot. The hypothefis that 
has been thought the mofl fatisfadory is 
that of Mr. Macquer, who fuppofes that,, 
in thefe circimiftances, an union is formed 
between the pure nitrous acid and phlogif- 
ton, fimilar to that which is formed between 
the vitriolic acid and phlogifton in the 
compolition of fulphur. He therefore fup- 
pofes that, in this cafe, a nitrous fulphur 
is formed, and that this fubftance is of fo 
inflammable a nature, that it cannot exift a 
moment without adlual ignition. 

But I would obferve that, fuppofing this 
hypothetical nitrous fulphur to be a<£lually 
formed, yet if it refemble other combufti- 
ble fubilances, the vitriolic fulphur for in- 
ftance, or any other whatever, in a property 
that is common to them all without excep- 
tion, it cannot be inflamed but in contad: 
with air ; which, according to concluiions 
clearly drawn from my experiments, and 
all other obfervations, is faturated with 
phlogiflion by the procefs, and when 
faturated can take no more, let the fub- 


256 Ohfewatlons on 

ftance that is heated in it be ever fo 
combuftible ; and confequently, in thofe 
circumftances, all inflammation muft be im- 
poffible. Whereas Mr. Macquer acknow- 
ledges, that this nitrous fulphur is capable 
of the moft violent inflammation in the clofeffc 
veflels, where there is no accefs of air, and 
it is well known that compofltions of gun- 
powder are made to burn even under water. 
Now the dod:rine of dephlogifl:icated air 
fupplies the eaiiefl: folution imaginable of 
this very difficult phenomenon. For it ap- 
pears that the nitrous acid cannot be heated 
to a certain degree, in contad: with any 
earthy matter, without producing dephlo- 
gifliicated air; by the help of which all 
combuftible fubftances burn with the greatefl; 
violence, much more than they can be made 
to burn with in common air. Here then I 
fuppofe that the moment the acid of nitre, 
contained in the nitre, and the earth of the 
coal, for example, thrown into it become 
red hot, in contad: with each other, dephlo- 
gifticated air is produced; and in this 
air the remainder of the charcoal, being 


Dephlogtfticated Air. ±^y^. 

likewife red hot, burns with the violence that 
is obfervable in the experiment^ while, at 
the fame time, other portions of the nitrous 
acid, are forming, with other parts of the 
fame decompofed charcoal, the union that 
conftitutes more dephlogifticated air; and 
thus the detonation continues, till all the 
charcoal, or all the nitre, is confumed ; the 
acid not being Z^/?, as fome chemiils exprefs 
it, but entering into; the compoiition either 
of the dephlogifticated air, or of fome other 
kind of air, that may be generated in the 

Let any perfon but attend to the pheno- 
mena of the detonation of charcoal in nitre, 
and that of the dipping a piece of hot char- 
coal into a jar of dephlogifticated air, and I " 
think it will be impoffible for him not to 
conclude that the appearances are the very 
fame, and muft have the fame caufe. There 
is the fame intenfe incandefcence, an de 
fame rapid confumption of the charcoal in 
both cafes ; and this is evidently owing to 
the eagernefs, as I may fay, with which this 
fpecies of air, the moil free from phlogifton 

S itfelf. 

258 Obfervatlons on 

itfelf, feizes upon the phlogifton of other 
bodies, in a fufficient degree of heat. Such 
appearances cannot be produced in common 
air, which, being more than half faturated 
with phlogifton already, can take but little 
more -, and therefore, to produce an appear- 
ance any thing refembling them, we are ob- 
liged to fupply the fire with a current of 
frefh air thrown into it by bellows. But 
fupplying a fire in the fame manner with a 
current of dephlog-ifticated air, which I have 
fometimes done, has a moft ailonifhing 
effed: of the fame kind, as I have obferved 
in my former publications on this fubjedr. 

This method of explaining the detonation, 
of nitre had occurred to me at the time of 
my firfl publication on the fubjedt, and a 
rhort hint of it, with a view to what be- 
comes of the acid of nitre, will be found iri 
my 2d volume, p. 60 j but I thought it 
might be ufeful to give a more general ac- 
count of it here. Many other important 
phenomena in chemiftry will, I doubt not, 
admit of the greatefi: illuflration from this 
difcovery ; but my acquaintance with che- 
2 miflry 

Dephlogifiicated Air. 259 

jiliftry being very partial, fuch illustrations 
are not fo likely to occur to me as they are 
to many other perfons. 

As to the nitrous fulphur of Mr. Macquef, 
I know of nothing more nearly approaching 
to it than nitrous air, which Confifls chiefly, 
if not wholly^ of pure nitrous acid, and 
phlogifton^ without any water. This, at 
leaft, is fimilar to the compolition of vitrio- 
lic acid air, which a continued heat in a 
confined Aate changes into folid fulphur. 

I fhall conclude this article of deplogifti- 
cated air and detonation, with an account of 
a very ftriking experiment that I made with 
Mr. Bewly's pyrophorus, the receipt for 
which will be found in my third volume, 
p. 402, and which, 1 make no doubt, may 
be made with any good pyrophorus. I put a 
quantity of it into one of the fmall jars 
which I ufe for experiments on air in quick- 
filver; then, filling up the vefilcl with 
quickfilver, I inverted it in a bafon of the 
fame, and threw up dephlogifticated air at 
different times. It always occafioned a fud- 
den and vehement accenfion, like the flaih- 

S 2 ing 

26o Ohfervations on 

ing of gunpowder, and the air was greatly, 

diminiflied, as might have been forefeen. 


Of the Prejence of Earth in atmofpherkal 
Airy or in dephlogijlicated Air^ as the pro^ 
per Origin and Bajis of it, 

"AVING never failed to get dephlo- 
gifticated air from earth and fpirit of 
nitre, and none at all from pure fpirit of nitre 
itfelf, I concluded that dephlogifticated air, 
and confequently atmofpherical air^ which is 
only dephlogifticated air in a ilate of deprava- 
tion,, coniifts of earth and fpirit of nitre 
The acid, I lince conclude, is not the acid 
of nitre as fuch, but an acid principle com- 
mon to it and the vitriolic acid, or an acid 
of which thofe two mineral acids are only 
different modifications. The Abbe Fon- 
tana and Mr. Lavoiiier, however, deny the 
prefence of earth in dephlogifticated air^ 
frcxoi having revivified,, as they fay, the 


- Dephlogijilcated Air. 261 

whole of a quantity of mercury diffolved in 
ipirit of nitre, after it had yielded a great 
quantity of both nitrous and dephlogifti- 
cated air. Coul-d this refult be depended 
upon, it would i:ertarnly follow, that there 
could be no earth either in nitrous, or in 
dephlogiflicated air. 

The account of their experiments I did 
not receive till my third volume on the 
fubjedl of air was printed off. I had time, 
how'ever, to repeat the experiments with 
fome attention, and to give an account of 
the refult of them in the preface to that 
volume. At that time I had found a clear 
lofs of li. dwt. from 17 dwt. 13 gr. of 
pure mercury, and I therefore concluded 
that fo much of the calx of the mercury 
entered into the compofition of the nitrous 
or dephlogiflicated air. I have fince had 
leifure to make this experiment with more 
attention than I was able to give to it be- 
fore ; and of the many that I made with 
this view, I fliall recite the particulars of 
two, becaufe feveral things occurred in 
them that may be worth notice, though 
S 1 the 

262 Ohfervations on 

the general refult was nearly the fame with 

that of which a report has been made 


I diffolved 1 7 dwt. 1 3 gr. of pure mer- 
cury, furnifhed me by Mr. Woulfe, in an 
equal weight of ftrong fpirit of nitre, and 
diftilled it to drynefs in a glafs retort with a 
long neck, bent fo as to be immerfed in 
water; the folution having been made in the 
fame retort, without ever being taken out 
of it. Then, giving it a very ftrong heat 
in Tand, all the mercury that was revivified 
came over; and being carefully coUedted, 
there appeared to have been a lofs of i-i dwt. 
very nearly. Making every allowance, I 
believe there was a clear lofs of i dwt. 
6 gr. 

In thefe experiments there are, however, 
four caufes of inaccuracy ; the firft arifing 
from the quantity of folid matter that 
comes over diffolved in the liquid that is 
procured during the firft produdlion of ni- 
trous air 3 the fecond from the liquid that is 
diflilled in bringing the whole to a folid 
mafs ; the third in the folid matter that 


Dephlogifiicated Air. 263 

fublimes in the neck of the retort durins: 
the revivification of the mercury ; and the 
fourth in the white matter that clouds the 
air, efpecially when it is produced with 
rapidity. AU thefe caufes of error I at- 
tended to feparately, and found only the 
firft and third to be at ^11 confiderable. 
After having found by experiment the 
amount of the lofs in all thefe cafes, I ilill 
found a confiderable deficiency in the 
weight qf mercury after the experiment i 
and therefore ftill conclude, that there is 
fome earth in the air; but I do not fay 
whether this earth be efiTential in its confti- 
tution, though I fufped: it to be fo, or only 
dijfohed in it, and foreign to it, like wateij: 
jin air. 

I diflblved in fpirit of nitre iB dv^t. 
19 gr. of quickfilver which had been dif- 
folved and revivified again many times in 
former experiments, fo that its purity may 
certainly be depended upon, and catching 
the liquor that diftilled over all the time that 
the nitrous air was produced, I found that 
when it was evaporated, cryftalized, and 
S 4 - dried 

264 Obfefvations on 

dried again, it weighed 3 dw. 15 gr; Put- 
ting this into a tall glafs phial, and ex- 
pofing it to a red fand heat, part of it was 
fublimed, coating thie glafs in circular 
fpaces with- a coloured matter, in the fol- 
lowing order, from the bottom, yellow, red, 
yellow, green, whitijh. The part which 
was not fublimed was of a beautiful light 
red, and weighed 2 dw. 12 gr. Scraping oiF 
the part that had fublimed, and efpecially 
the green, which was moft copious, the 
whole, when mixed together, appeared m. 
the form of a dirty brown, or yellowifh 
matter, like Scotch fnuff, weighing 12 gr. 
By trituration it yielded a good deal of 

Taking all the precipitate, and mixing 
with it that which had been collected from 
the liquor that had diftilled over during the 
folution, as mentioned above, and putting 
it into a retort, I expofed it to as much 
heat as the glafs would bear in a naked fire, 
and continued the diHillation till nothing 
but a whitifh flain was left at the bottom 
of the retort, and a very little yelloviiiili 


Dephlogifiicated Air, 265 

matter adhered clofely- to the fides of it, 
which Gould not be fuppofed to weigh 
more than a couple of grains. Colle(fting all 
the quickfilver, it weighed 17 dw. 18 gr; 
fo that there had been a lofs of one dwt. 
• In this manner cif making the experiment, 
the quality that fublimes is much lefs than 
ufiial. -That the folid matter contained in 
the liquor that comes over- during the dif- 
tillation of the folution to drynefs, after 
the produ(5li6n of nitrous air, is incon- 
fiderable, and may be negledied, appeared 
from the following obfervation. I received 
in a cup all the liquor that came over in a 
procefs of this kind, obferving that, at iirft, 
it was blue, but prefently became colour- 
lefs, by being expofed to the open air -, but 
at laft it was ftrong yellow fpirit of nitre. 
This liquor expofed to a gentle heat intirely 
evaporated, having only an exceedingly flight 
yellow ftain at the bottom of the earthen 
Clip in which the evaporation was made. 

As to the whitifh matter that clouds the 
air, it is, when colleded, fo very incon- 
fiderable with refped to weight, that it may 


$66 Ohfern^attons on 

be very fafely negledled. However in one 
of my procelTes, all the particulars of which 
I do not think it worth while to recite, I 
carefully attended to this circumftance, 
making the procefs in fuch a manaer, that 
^11 the air, except a very little in the niid^ 
die of the procefs, came over without any 
turbid appearance whatever, and ilill the 
refult was nearly the fame as that of the 

In one of thefe proceffes I obferved that 
twice as much nitrous air was got from the 
folution of mercury after it was com- 
pletely diflblved, as during the folution, 
and the dephlogifticated air was about three 
times a3 much as the nitrous. 

It will appear from the above recited ex- 
periment, that confidering the quantity of 
air, both nitrous and dephlogifticated, pro- 
cured by the folution and revivification of 
the mercury, and the fmall lofs of mercury 
in the procefs, that by far the greateft part 
of the weight of air muft come from the 
ncid of which it confifls, the earth bearing 
but a fmall proportion to it. 


Defhlogljlicated Air, 267 

After the preceding experiments, I 
thought it might be poffible to difcover 
the earth which is in air, by decompoling 
a quantity of dephlogiflicated and nitrous 
air in the fame pure water, which muft, of 
courfe, retain all that is folid in either of 
them. Accordingly I decompofed thirty ninQ 
ounce meafures of nitrous air, and nineteen 
of dephlogiflicated air, throwing out, at 
different times, fix ounce meafures of 
phlogiflicated air, in little more than two 
ounces of diflilled water, which became 
a volatile fpirit of nitre by the procefs. 
There was no turbidnefs or any earthy 
matter vifible in it; but, evaporating it to 
drynefs, there remained three or four grains 
of a red or dark brown earthy fubflance, part 
of which was inflantly diffolved in fpirit of 
fait, and gave it a brown colour. Part of 
it I expofed in the open air, from which it 
attracted moiflure. Poflibly, however, the 
folid matter in this water might be fo in- 
corporated with it, as to be evaporated 
along with it -, for I made it boil during 
|he evaporation, Confidering the quantity 


S68 Obfervattons on 

of earthy matter that remains after the dif- 

tillation of the pureft water, the refiduum 

in this experiment will be thought incon- 

iiderable; and I own it did not anfwer my 


With a view to prevent the liquor in w-hich 
was the mixture of nitrous and dephlo- 
giflicated air from becoming acid, I re- 
peated this procefs in cauftic alkali (though 
I found afterwards that, by long keeping, 
it had imbibed a good deal of fixed air) 
when the appearances were piealing enough, 
and the refult rather favourable to the fup- 
pofition of the prefence of earth in air. 
Immediately on mixing thefe two kinds of 
air over this alkaline liquor, there was a 
beautiful precipitation of white vapour, and 
again when the faturation was nearly com- 
pleted j but there was little or nothing of 
this appearance in the middle of the pro- 
cefs. Pouring the alkali, after this, into 
another veflel, a denfe white vapour i/Tued 
from it. All thefe appearances were more 
flriking after I had repeated the procefs 
feveral times in the fame alkali. After the 


Dephlogffiicated Air, 269 

whole procefs the li(juor had acquired a yel- 
lowifh colour. 

This experiment was made on the 19th 
of September 1777, ^^^ looking at the al- 
kaline liquor on the 14th of December 
1778, I obferved that a white matter was 
depofited from it j but whether this came 
from the air that was decompofed in it, or 
not, I do not pretend to fay. 


Various Obfervations relating to the Dhninu* 
tion of common Air, 

I . Of the Purify of Air in different Cir^ 

WHEN r firfl difcovered the pro- 
perty of nitrous air as a teft of the 
wholefomenefs of common air, I flattered 
myfelf that it might be of conliderable 
pradical ufe, and particularly that the air 
of diftant places and countries might be 
brought and examined together, with great 
eafe and fatisfadlion \ but I own that 
hitherto I have rather been difappointed in 


270 Obfervations on 

my expedtations from it. My own obfef- 
vations have not, indeed, been many^ but 
according to them the difference of the 
open air in different places, as indicated by 
a mixture of nitrous air, is generally incon- 
fiderable ; and I have reafon to think that 
when very unw^holefome air is conveyed to a 
great diflance, and much time elapfes be- 
fore it is tried, it approaches, by fome 
means or other, to th^ flate of wholefome 
air. At leaft fuch I have found to be the 
worft air that has at any time been fent to 
ihe in Wiltihire from diflant manufacturing 
towns and workfhops &c. in them, where 
the air was thought to be peculiarly un- 
wholefome. I am fatisfied, however, from 
my own obfervations, that air may be very 
offenfive to the noftrils, probably hurtful to 
the lungs, and perhaps alfo in confequence 
of the prefence of phlogiflic matter in it, 
without the phlogiflon being fo far incor^ 
porated with it, as to be difcoverable by the 
mixture of nitrous air. 

I gave feveral of my friends the trouble 
to fend me air from diflant places, efpecially, 


Dephlogijiicated Air, ^yi 

from manufafturing towns, and the worft 
they could find to be ad:ually breathed by 
the manufadlurers, fuch as is known to be 
exceedingly offenlive to thofe who viiit 
them ', but when I examined thofe fpeci-« 
mens of air in Wiltfhire, the difference 
between them and the very befl air in this 
county, which is efleemed to be very good, 
as alfo the difference between them and 
(pecimens of the beft air in the counties 
in which thofe manufaduring towns are 
fituated, was very trifling. 

Mr. Boulton of Birmingham was {q^ 
obliging as to fend me a great variety of 
fpecimens of air from that manufacSluring 
town, along with an account of his own 
examination of them by the teft of nitrous 
air. I fhall only note his account of four 
of the fpecimens, including the beft and 
the worfl, and reducing his numbers to 
my own. 


272. Obfervations on 

The aip in a garden near the Meafures. 

new church i.^^ 

The bottom of the old church 

fleps, very low and clofe 
The middle of Mr. Taylor's ma- > 1.4^ 

nufadtory | 

The Horn Button- manufadory -* 

When I examined them myfelf, on the 
1 2th of December 1777, the former was 
as nearly as poffible the fame with the air 
of pretty high ground in Wiltfhire ; fo 
that the difference between the worft air in 
the manufadturies at Birmingham and very 
good air was .06. On the 3d of July fol- 
lowing, I examined the remainder of the 
fame fpecimens of air again, and found the 
difference between them and good air to 
be .02 ', and at the end of Odober it was 
only .01. 

Dr. Percival alfo was fo good as to fend 
me feveral fpecimens of air from Manchef- 
ter, and one from his country houfe at 
Hart-hill, about three miles from Man- 
chefter, the higheft and healthiell fituation 
4 in 

Cvmmon Air* 27 j 

in fhat part of the country. The air of 
this place was nearly the fame with that of 
Wiltfhire^ and when I examined the fpe- 
cimens he fent me on the 3d of July 1778, 
the meafures of the teil for this air were 
1 . 27, of the air from a weaving fhop m 
Manchefter 1.305, and of the marketplace 
1.295, '^^^ difference therefore between 
the former and pure air was only ,035, and 
of the latter only .025. 

The worit air that I have yet found 
breathed by men, and that was fent from a 
diftance, was from a coal-pit in the neigh- 
bourhood of Briilol. For the difference 
between good air and that which was taken 
in the fhaft of the pit ten yards below the 
mouth was .07, and between the fanie and 
that which was taken where the men were 
at work was,2i. 

Mr. William Vaughan took the trouble 
to procure me a fpecimen of air from a 
calico printing houfe, which was exceed- 
ingly offenlive, and I have no doubt of its 
having been taken very properly, and having 
been well fecured from all communication 
T with 

;a74 Ohfervations on 

with the external air -, and yet when I exa- 
mined it in Wiltfhire the difference between 
it and good common air was only .02. 

Mr. S. Vaughan, fenior, on his paffage 
from Jamaica, brought me two bottles of 
air, one from the hold of the fhip, intole- 
rably oiFenfive, the other the frefh air above 
deck in about 30"^ N 3 but the difference be- 
tween thefe fpecimens of air, and the air 
of Wiltfhire, was quite inconfiderable. 

I have frequently taken the open air in 
the moil: expofed places in this country at 
different times of the year, and in different 
flates of the weather y &c. but never found 
the difference fo great, as the inaccuracy 
arifmg from the method of making the 
trial might eafi]y amount to, or exceed. 

2. Of the State of the Air //z Hot- 
house s. 

There is generally a fenfe of oppreflion, 
or difficult refpiration, felt on entering a 
hot houfe, which feems to proceed from 
fomething different from mere heat 5 for 
we feel nothing of that fenfatlon in an 


Common Air, 275 

^ually w^rtn, well aired room i but my 
obfervations on this kind of air would not 
have indicated any fuch thing. On the 
3d of June 177B, I took the air in three 
feveral hot houfes adjoining to each other, 
but having > different degrees of heat, and 
found tl'iat one meafure of that air and one. 
of nitrous air occupied the fpace of 1.29 
meafures ; when the refult of the fame 
experiment with the external air, taken at 
fame time, was 1.27, a difference certainly 
very inconliderable. 

3. Of the EffeB of the Perspiration of 
the Body on Air. 

That breathing contaminates air is well 
known, and this makes a difference in air 
that is eafily diltinguifhed by a mixture of 
nitrous air. Having obferved this, I had 
, the curiofity to try whether air was injured 
in the fame manner by any effluvia attend- 
ing the fenfible, or infenfible, perjpiration 
of the covered parts of the bodyjj and, 
with refpe<a to myfelf I think I have given 
T 2 it 

276 ■ Obfer'vations on 

it a very fair trial, and can alTert, that t 
never found air to be at all fenlibly injured 
in thofe circumftances, but rather, if I 
could depend upon my application of the 
tell of nitrous air for fo fmall a difference, 
it was fomething better than the external 
air. I have fat an hour v\rith my ivxn in a 
trough of very warm water, and my warm 
hand in a glafs jar placed with its mouth 
in the water (my hand, of courfe, per- 
fpiring, though infenfibly, all that time) 
but when I examined the air within the 
jar immediately afterwards, it appeared not 
to have been the leafl injured by the 

But what I exped:ed to produce a much 
more fenlible change in the air was the 
perfpiration under the arm pits, after walk- 
ing, or uiing much exercife. For this 
purpofe, I have fometimes introduced phi- 
als of warm water, and poured it out, when 
I had introduced my hand as carefully as 
poilible into the place j but at other tirqes 
I have put open phials, with perforations 
in the bottoms, and alfo open glafs tubes, 


Common Air. 277 

three or four inches long, the orifices of 
which were fuch as that I could ealily cover 
them with my thumb or finger. This 
appearing to be the faireft method of all, I 
made the greateil ufe of it. . For the air 
within the open tube muft certainly, in 
the courfe of an hour or two, become of 
the fame quality with the air on the outfide 
of it. In thefe trials alfo, I have preferred 
walking to any other kind of exercife, though 
I have tried feveral methods j becaufe, in 
walking, little or no motion is given to 
the air about the arm; and it is very eaiy. 
to introduce one's hand, and, covering 
both the ends of the tube at the fame time, 
to be quite fure that the air within the 
tube is in that Hate to which the perfpira- 
tion of the body had reduced it. But 
ftill, after walking a long time, and making 
myfelf purpofely as hot as pofiible, I have 
never found the air within the tubes in the 
leafl: degree worfe than the external air; 
but, as I have faid before, fometimes feem- 
ingly a little better. 

T 7 The 

27S " Ohfervations on 

The experiment of this kitid that I 
made with the moiib care Was in pretty hot 
weather, on the 4th of June 1778. I put 
fuch tubes as I have mentioned above under 
each of my arms, and after firft work- 
ing with a fpade, and then walking about 
three miles, in which exercifes I ptirpofely 
made myfelf exceedingly hot, I withdrew 
the tubes with as much care as a good deal 
of experience had taught me, and I found that 
6ne meafure of this air and one of nitrous 
air occupied the fpace of 1.267 meafures ; 
when the fame experiment being made 
with the befl: external air on the fame day, 
the meafures were 1.28. Every circumftance 
in the application of the teil: was, as near a^ 
I could make it, the very fame in both 

4. Of the State of the Air in Dining- 

Large and lofty rooms are generally pre- 
ferable to fmall and low ones. But this i§ 
only the cafe when the fame company con- 
fin*^ themfelves in it the fame fpace of 


• Common Atr. ' 279 

time, with the doors, &c. ihuti for, hav- 
ing more air to breathe, it will certainly 
require more time to contaminate it. But 
when the company is larger or procefles are 
^oing on that will efieiftually contaminate 
the air (as many candles burning in the 
room, hot vi(ftuals, continuing a long 
time upon the table, &c.) a finall room is 
much preferable, unlefs there be an open- 
ing in the top of the large room, that will 
eaiily promote a change of air in it. Be-» 
caufe the occafional opening of the door 
in a fmall room will generally pro- 
duce a fufficient change of a great part of 
the air -, whereas the height of the door 
bearing but a final! propoition to the height 
of a large and well proportioned dining 
room, the opening of the door^ or evea 
its continuing open, has very little effed:. 
/The extreme offenfivenefs of the air m 
thefe circumitances is not perceived by per- 
fons who fit in it from the beginning, hut 
it is immediately perceived by perfons who 
ftep out of the room, and return to it» 

T 4 Dining 

23o Qbfervations on 

Dining one time a in company of not 
more than eight or ten perfons, in a large 
and very lofty room; and being called out 
prefently after the cloth was removed, I 
was much ftruck with the ofFenfivenefs 
of the air on my return j and being willing 
to afcertain the degree in v/hich it was in- 
jured, I took occalion, on fome pretence or 
other, to pour the water from one full de- 
canter into another, and putting in the 
flopper, faw that no body opened it till the 
company feparated. I then took the de^ 
canter into my laboratory, and examined the 
air at my leifure \ when it appeared to be 
much contaminated. For one meafure of 
this air, and one of nitrous air occupied 
the fpace of one 1.31 meafures -, when the 
fame experiment being made with the air 
of a well ventulated room in the fame 
houfe, the meafures were 1.25. At the 
fame time I breathed a quantity of air til4 
it jufl: extinguifhed a candle, and found 
that the meafures were 1.43. So that, 
had the air of the dining room received a 
little more than twice as much more phlo- 


Common Air. 281 

giftic matter, as it was charged with by the 
breathing of thefe eight or ten perfons, the 
effluvia of the victuals, &c. a candle would 
not have burned in the room. I would ad-^ 
vife, therefore, that when fuch large din- 
ing rooms are built, provifion be made for 
letting out the vitiated air at the top of 
them. For breathing fuch contaminated 
air fo long a time as it is now the cuflom 
to do, at and after dinner, muft be very 
hurtful. Otherwife, if it were not incon- 
venient on other accounts, it would be bet- 
ter to have the dinner in one room, and 
the defert in another. 

5. Of the EffeB of Stea-m on Air, 

Very early in the courfe of my obferva* 
tions concerning air, I found that the agi- 
tation of any kind of noxious air in wafer 
purified it to a certain degree, as alfo that 
the agitation of pure air in water depraved 
it fo much, as to bring it to about the fame 
ftandard, ijiz. that in which a candle juft 
goes out. It might, therefore, be thought, 
t\i2it Jieam, or the vapour of water, inti- 

2S2 Obpriidtkfis oil 

mdtely diifufed through a quantity of noxi- 
i>tfs air, Avould much foonref imbibe the 
rphlagifton with which it was charged 5 and 
•feverai iperfons, particularly Mr. Keir, have 
even thought that the melioration of air by 
vegetation may be owing to the exhalation 
of moiilure from plants in a vegetating fbate. 
i was "vety willing to adopt that ideamyfelf, 
in preference to my own^ which was that 
■plants imbibe the phlogifton with which 
•the air is overcharged intv their fubji once, 
^nd convert it. into their proper nourifh- 
ment. But when I tried the effects of fleam 
on phlogiflicated air, with as much at- 
tention as I could give to the experiments, 
I never found that it Was at all mended by 
the procefs. -^ 

I firfl took-.a quantity of air that had been 
phlogiflicated by a mixture of iron filings 
and brimftone^ and introducing into it the 
end of a glafs tube, communicating with a 
phial, v^hich I had filled -With water, I 
kept it in a boiling heat, about a quarter of 
•iin hour, in which time the ileam had 
efedually pervaded tlie mafs of air, having 
'' - ' made 

• Common Air, ^8^ 

m^ade the jar in which it was contained 
thoroughly hot, and having expelled three 
fourths of it. Bui what Temain^d of this 
air was no mor-e diminished by nitrous air 
than it had been before. 

Afterwards I feveral times filled jars with 
air phlogiflicated with nitrous air, and alfo 
by other means; and placing them, in- 
verted, in pans of water, made the water 
boil a long time, till a great part of the air 
was expelled by the fteam, but I never 
found the air fo expofed to fteam to be at 
all mended by it. Common air was always 
fenfibly injured by this procefs, as might 
have been expected from my former experi- 

I am willing to think, however, from 
the obfervation of Mr, Arden, an intelli- 
gent lecturer in natural philofcphy, who 
firft mentioned the obfervation tome, as hi^ 
own, that fteam, or the vapour of water, 
may unite v/ith fomething or other that 
makes air oftenfive, and help to fweeten it ; 
or, at leaft, that throwing a quantity of 
ileam into a room in which the air is oifen- 
3 live 

284 Obfer'uations on 

live may promote a change of the air, fo as 
to be an eafy and valuable remedy in fuch 
cafes. He has mentioned to me feveral ex- 
periments of his own, as well as obferva- 
tions of other perfons, that make it very 

6. Of the EffeB of the Electric 
Spark on common Air. 

In the preface to my third volume of 
Ohfervations on Air, I mentioned the re- 
fult i^f feveral experiments on taking the 
eleBric fpark in common air. I have fince 
purfucd this fubjed: a little farther, with 
a. view to fome peculiar circumftances at- 
tending the diminution of the air in this 
procefs, and the depolit of an acid from it. 
But before I recite the obfervations, I can- 
not help expreffing my concern that feveral 
perfons have not been able to fucceed in the 
fimple experiment of the diminution of air 
hy the eledtric fpark, and changing the 
colour of the juice of turnfole over which 
the diminution is made. For the iktisfac- 
tion of fuch perfons, I fliall recite all the 


Comm$n Air. 285 

circumftances neceffary to be attended to in 
it, as I repeated the experiment in the 
prefence of Mr. Magellan and Mr. Nairne, 
who carefully attended to the whole pro- 

Having nearly filled a glafs tube about a 
tenth of an inch in diameter, open at one end, 
and having a piece of iron wire cemented 
in the other, with water tinged blue 
with the juice of turnfole (having pre- 
viouily expelled the air by means of an air 
pump, fo as to leave about three fourths of 
an inch of air in the tube) we took the 
electric fpark in it, till the air was con- 
fiderably diminiflied, and the liquor turned 
red. We then expelled the red liquor by 
means of the air pump, expanding the air, 
and admitted more blue liquor ; and then 
we repeated the eledirification till the dimi- 
nution had proceeded as far as it would, 
which was about one fourth of the whole 
bulk of the air. Then, admitting the 
bliie liquor again, the machine, which was 
a very powerful one (conftrudted by Mr. 
Nairne for Lor4Shelburne) a full half hour, 
I without 

286 Ohfervations on 

without being able to efFes^l the leafl far- 
ther diminution of the air, or the leail 
fenfible change in the colour of the blu,e 
liquor. They were both fatisfied that no 
experiment could be made with greater 

I Ihall now proceed to mention other 
circumflances attending this procefs. . 

I took thq eledlric fpark in common air 
confined by quickiilver; ajid then, £tdmit- 
ting to it water tinged blue with the juice 
of turnfole, it became red in the fpace of 
a day and two nights, but the colour did 
not change prefently. Alfo, after this the 
diminution waa- greater than it had been 

. Having taken the eledric fpark in com- 
mon air upon quickiilver, as before, it was 
prefently diminiihed as ufual ; and the next 
day without any farther eledrification, the 
diminution v/as more confiderable. The 
third day I admitted to it the juice of turn- 
fole, aa4. in about an hour it appeared to 
be red at the top, but was not feniibly 
diminiihed more than before. In lefs than 

a day 

Commpn ^ir* z^f, 

a day, it. became, wholly red,, and. thep, no 
farther diminution was apparent. 

I took, a quantity of water which had 
been made blue with the juiCe of turnfole, 
and which had been . made feemingly red 
with the eledric fpark, taken . in the conir 
mon air over it; hut, on mixing all the 
parts of it together, it refumed its. blue co- 
lour (the blue colouring matter having only 
fubnded to the bottom) fo that altera- 
tion in the conflitution of this liquor by 
this procefs, though manifefh to the eye, 
is not, in fa^l, fo very conliderable. It is 
evident, however, from the preceding ob- 
fervations, that it could not be the mere 
co,ncu£ion given, to the air by the fpark, or 
{hock, that had thi^ eifed: upon it ; becaufe 
when the air was completely diminifhed, 
the fpark or fhock had no efFedt, and the 
liquor turned red when it was admitted to 
the air a long time after the operation of 
the elcdlric fpark upon it, while it was 
confined by quicklilver. This circum.fl.a.ncQ 
may deferve farther invefllgation., 


2S8 Ohfervafions on 

y. Of the effeSt of the Calces of Copper 
and Iron on Air. 

Several properties of metallic calces 
may be difcovered by their expofure to 
the common air. I have made fome ob- 
fervations v^^hich may be pleafmg and fatis- 
fadlory with refpedt to thofe of copper and 
iron. They prove that the blue colour ac- 
quired by the former, and the red colour 
acquired by the latter, are owing to the 
dephlogiilication of them. For thefe co- 
lours cannot be affumed by them but in the 
open air, and the air to which they are ex- 
pofed is more or lefs phlogifticated by this 

I dilTolved copper in a folution of fal- 
ammoniac, and confined the folution in a 
phial with a ground ftopper. After a day 
or two, when the folution was become 
thoroughly blue, I examined the air within 
the phial, and found it to be confiderably 
worfe than it had been. For one meafure 
of it and one of nitrous air occupied the 
fpace of 1.33 meafures 5 when the com- 
ipon air at the fame time was diminiflied by 


Common Air, 289 

the nitrous air fo much, that the fame 
quantities occupied the fpace of little more 
than I.I meafures. At another time I 
covered a phial containing a quantity of 
this folution with a fmall jar {landing in a 
trough of water, and found, after a few 
days, though not more than half the folu- 
tion, beginning from the top, had turned blue, 
that the air to which it had been expofed 
was almoft completely phlogifticated. 

Pouring a diluted folution of. pearf aflies 
into a diluted folution oi green vitriol \N\\h. 
a funnel, that the common air within the 
phial might mix as little as poiTible with 
the open air, the precipitate was at firfl of 
a light blue ; but by expofure to the air it 
became firft of a deep indigo blue, and then 
a red. 

Covering a quantity of this bjue pre- 
cipitate contained in a glafs cupy with a 
glafs jar ftanding in watery I.obferved that, 
after twp or three days, all the furface of 
the precipitate, though covered with water, 
was become red. When. I flirred it up, all 
below the furface was as blue as ever. In 

y this 

290 Ohfervations on 

this flate I examined the air, and found it 
fenfibly phlogifticated, though not to a 
great degree. 

Having made another blue precipitate of 
iron, I poured it into a fmall retort, and 
turning it every way, to give all the infide 
a coating of it, I expofed it to the heat of the 
fire, till it was become partially red (for I 
did not perceive it would become wholly 
fo) and, examining the air in the infide, I 
found that One meafure of it and one of 
nitrous air occupied the fpace of 1.3 
meafures; when the fame quantities of 
common air and the fame of nitrous air oc- 
cupied the fpace of 1.24 mcafures. 

Laftly, to give the calx of iron more 
time to affed; the air, I made the mixture in 
a phial which I left half full of air -, and in 
a few days the furface of the water was 
covered with a red pellicle, and fome time 
afterwards the furface alfo of the precipi- 
tate at the bottom of the phial, which had 
been of a deep blue, was become red. 
After waiting three weeks, I examined the 
air, and found it fo much phlogifticated, 


Common Air, 291 

that one meafure of it and one of nitrous 
air occupied the fpace of 1.55 meafures. 

Having alfo coated the inlide of a glafs 
tube with the green precipitate, I let it iland 
near three weeks with its orifice immerfed 
In water, in which time it had become 
nearly red ; and then examining the air, I 
found no fixed air in it (which might have 
been fufped:ed to come from the pearl 
afhes efpecially ; and thus to have injured 
the air, without any proper phlogiftica- 
tion) and one meafure of it and one of 
nitrous air occupied the fpace of 1.45 
meafures. In this experiment, therefore, 
there was a proper phlogiftication of the 
common air, without any thing from the 
alkaline falts. 

It is not a little remarkable, that this 
change of colour will take place though the 
precipitate be covered with a large body of 
water. I have found it when it was co- 
vered to the depth of eleven inches, which 
is that of the trough in which I ufually 
make my experiments. It was at firft all 
blue, the next day I found the furface 
U 2 com- 

292 Ohfervations on 

completely red/ when the bottom was as 
deep a blue as ever. This refembles the 
property Qi ferum in my experiments on 
blood. For as that liquor admits phlogiflon 
topafs from the blood to the air, fo water 
permits ' phlogiflon to pais from this pre- 
cipitated calx to the air. 

The refult of thefe experiments will be 
^ dijfferent according to the degree of fatura- 
" tion in the foliition, and perhaps according 
to other circumftances. ' • 

At the fame time that I got the deep blue 
precipitate, with which I made feveral of 
'the experiments above-mentioned, I mixed 
a quantity of the faturated folutions, both 
of the vitriol and of the pearl aflies; in an 
open jar, and the whole became red at'once, 
without my being able to perceive any pre- 
vious blue colour at all. Sometimes the 
precipitate will be wl)ite, or grey, efpecially 
when the folution of the iron is poured into 
that of the alkali: In this cafe the firfl 
change is to a very light blue, then 'to a 
deeper blue, and laflly to' a red. 


Comman Air, 293 

In the kft experiment above-mentioned 
the air became phlogiilicated in confequence 
of the liquor to which it was expofed ac-^ 
quiring colour j whereas in the following it 
was injured at the fame time that the liquor 
loji its colour. I took a quantity of ipirit of 
fait made yellow by various impregnations, 
and then ^riade it colourlefs by liver of 
fulphur. After this I inverted tlie phial 
with common air in it, 2.TiA let it fiand 
about a week, obferving that In two days it 
had recovered its original yellow colour ^ 
and the air appeared to be fo much injured^ 
that one meafure of it and one of nitrous 
air occupied the (pace of 1^9 meafures* 
The phlogiflon that produced this effe<f^ 
came probably from the liver of fulphur. 

8. Air injured by the Efffimium of Water 
frejh dijtilkd. 

Notwithilanding it has been a maxim 
with chemifts, that water contrads no 
union with phlogifton, it is acknowledged 
that water fre{h diililled acquires fome tiling 
of an empyreumatic nature, which gives it 
U 3 ai3 

294 Ohfervations on 

an unpleafant flavour, and which goes ofF 
by expofure to the open air. That this 
volatile principle is phlogifton I afcertained 
by expoiing air to the influence of it. 

I took w^ater frefh difl:illed in copper, 
and filled a phial about half full of it, and 
examining the air w^ithin the phial about a 
month afterwards, I found it fo much 
phlogiflricated, that one meafure of it and 
one of nitrous air occupied the fpace of 
1.32 meafuresi when, with the fame nitrous 
air and common air, the fame meafures 
were 1.22. 

In this cafe it might be fufpeded that 
the phlogifton came from the copper. But 
at the fame time I made a iimilar experi- 
ment, with a flmilar refult, on water dif- 
tilled in glafs. In this cafe there was more 
air, and a fmaller quantity of water in the 
phial, but the time of expofure was nearly 
the fame 5 and with this air the meafures of 
the tefl were i ,26, It is probable that with 
more water, oipre time, and lefs air, the 
refult woul4 have been more conflderably 
Ixi favour of the water having acquired 


Common Air, 295 

phlogifton in the adt of evaporation, with- 
out any communication with fubftances 
that are thought to contain it. This ex- 
periment, however, is fufficiently iimilar 
to the others I have recited, in which mere 
heat had the fame efFedt as the commu- 
nication of phlogifton. But water, in this 
cafe, like the fpirit of nitre in the former, 
might contain phlogifton, and the evapora- 
tion might change the mode of its combina- 
tiony fo as to make it more eafy to be 
imparted to air. 

U 4 S E, C- 

296 Obfer vat ions on 


Obfervations relating to the. Melioration of 
Air by the Grov/th of Plants. 

IN my firfl: publication on the fubje<5l of 
air, I gave an account of feveral experi- 
ments by v/hich it appeared tliat air injured 
by rcfpiration, putrefadion, or the burning 
of candles, was unqueftionably reflored to a 
great degree of faiubrity by the growth of 
fprigs of mint, and other plants in it. At 
the fame time I mentioned other inftances, 
in which, to my great furprize, air, which 
I had imagined, from the appearance of the 
plants growing in it, mufl: have been in a 
mending llate, had not grown better at all, 
and had fome times grown much worfe. 
See Vol. I. p- 91? &c. 

Of the reftoration of air in v/hich can- 
dles had burned out to a (tate in which 
they burned very well in it again, I had 
many inftances in the years 1771, and 
1772, in the latter without a fmgle failure. 


J * 

Fegefafiorf, 297 

p. 53 ; and in the former year I recoiled: 
not more than one, not mentioned in my 
account, becaufe it was but one out of 
very many, and might eafily be accounted 
for without affediing the conclulion which 
I then drew from the whole, viz. that it 
is very probable, that the injury which is 
continually done to the atmofphere by the 
refpiration of fuch a number of animals as 
breathe it, and the putrefaftion of fuch vaft 
malfes both of vegetable and animal fub- 
flances expofed to it, is, in part at leafl, 
repaired by the vegetable creation. For if 
a plant be unhealthy, or if a few leaves 
drop off and putrefy, it will not only pre- 
vent the reftoration of the air, but vrill 
contribute to make it worfe. On account 
of this lingle failure, however, I did not 
make any conclufion, not even in favour 
of the probability of my hypothecs, till the 
year following, in which it fo happened 
that I had not one failure. 

Probable, however, as I thought it to 
be from the whole of my experiments, that 
vegetation tends to counteract the noxious 


298 Obfervations on 

effects of rejfpiration, putrefadion, and the 
burning of inflammable fubftances, by- 
plants inhaling the phlogifton thrown into 
the air by thefe proceflTes, I confidercd the 
fubjed (fee p. 92) as " well deferving a 
*' farther invelligation, as it might throw 
** light on the principles of vegetation.'* 
Such, however, has been my lituation and 
engagements lince that time, that till the 
year 1777, I never repeated any of my 
former experiments on this fubje<ft, though 
I always had it in contemplation, and meant 
to profecute them much farther than I had 
done before. 

Having heard that feveral perfons abroad 
had not been able to repeat my experiments 
with the fame fuccefs, I now refumed them j 
and when I had made fome progrefs in 
them I heard of the experiments of Mr. 
Scheele on beans, who reports the refult 
of them to have been conftantly the reverfe 
of mine. On this account I gave the 
more attention to this buiinefs in the 
Ipring and fummer of 1778 -, and though I 
was interrupted in the profecution of them, 

I madQ 

Vegetation B 299 

I made a confiderable number in the be- 
ginning of the fummer, the refult of which 
was as follows. 

1. In general, the experiments of this 
year were unfavourable to my former hypo- 
thelis. For whether I made the experi- 
ments with air injured by refpiration, the 
burning of candles, or any other phlogiilic 
procefs, it did not grow better but worfe; 
and the longer the plants continued in the 
air, the more phlogifticated it was. I alfo 
tried a great variety of plants, but with no 
better fuccefs, as fprigs of mint, fpinach, 
lettuce, onions, brooklime, and fome others. 
The method in which I ufed them was, 
generally, to put the roots into phials filled 
with earth and water, and then to intro- 
duce them through water into the jar 
containing the air on which I was making 
the experiment ; the jars being about ten 
inches in length, and two and a half in 

2. I have had feveral initances of the 
air being undoubtedly meliorated by this 
procefs, eipecially by the ihoots of ilraw- 


5^0 Ohfervattons on 

berries, and fome other plants, which I 
could, by bending, introduce into thci jars 
or phials of air, fupported near them in the 
garden, while the roots continued in the 
earth. This I thought to be the faireil 
metliod of trial, the plant growing, in 
every refped:, in its natural way, except that 
■part of the ilem was obliged to lie in water, 
and the flioot was in air, confined in a nar-? 
TOW jar, 

3. I had other inflances, no lefs un- 
queftionable, of common air not only re- 
ceiving no injury, but even confiderable 
advantage from the procefs -, having httn 
rendered in fome meafure dephlogifticated 
bj it, fo as to be much more diminifhed 
hy nitrous air than before ; a thing which 
I was faip from expecting ; having had 
nothing farther in view than limply to try 
whether the air would be- injured or not ; 
Mr. Scheele, who made his experiments 
With beans, having always found it in- 

4. In moil of the cafes in which the 
plants failed to meliorate the air, they 


Vegetation, 301 

were either manifeftly fickly, or at leaft did 
not grow and -thrive, as they did moft re- 
markably in my firil experiments at Leeds j 
the reafon of which I cannot difcover. 
Indeed, I did not at this time make ufe 
of any air tainted with putrefadlion, con- 
tenting myfelf with that which was in- 
jured by my own refpiration, or the burn- 
ing of candles; and it was in air tainted 
"wi-th the putrefaction of animal fubilances 
that my plants had flouriihed the moil. 
As to air injured by other proceiTes, as by 
iron filings and brimflone, or by nitrous 
air, I had not made trial of it before, except 
the latter, which I exprefsly faid (Vol. I. 
p. 119)- did not fail to kill the plant. 

In thofe inilances in w"hich the plants 
grew the bell, they v/ere, however, but 
fickly, as appeared by the leaves foon turn- 
ing yellow, and failing off when the leafl: 
motion was given to them. In fome cafes, 
however, as in. thofe mentioned in Vol. I. 
p. 91, I faw no particular reafon v/hy the 
air fhould not have been meliorated. 

3 ' Upon 

^02 Ohfervations on 

Upon the whole, I ftiil think it probable 
that the vegetation of healthy plants, grow- 
ing in iituations natural to them, has a 
falutary efFedt on the air in which they 
grow. For one clear inftance of the meli- 
oration of air in thefe circumftances fhould 
weigh againil a hundred cafes in which the 
air is made worfe by it, both on account of 
the many difadvantages under which all 
plants labour, in the circumftances in which 
thefe experiments muft be made, as well 
as the great attention, and many pre- 
cautions, that are requiiite in conducing 
fuch a prccefs. I know no experiments 
that require fo much care. Particularly, 
every thing tending to putrefcence, every 
yellow or ill-looking leaf, &c. muft be 
removed, before the air can have been in- 
jured by it, and I did not at this time watch 
my plants with fo very much attention as. I 
did when I firft made my experiments j 
though the method I now ufed in examin- 
ing the ftate of the air was much more 
exadt than ar^y that I was acquainted with at^. 
that early period of my ohfervations on air. 


Vegetation, ^03 

It was in June 1772, that I firft made 
nitrous air, and it was confiderably later in 
that year that I difcovered its property of 
ferving as a ready tefl: of the purity of com- 
mon air j whereas my experiments on plants 
were begun in 1 77 1 > and were refumed in 
June 1772. Alfo, after I had difcovered 
the ufe of nitrous air, as a tefl of the purity 
of other air, it was fome time before I hit 
upon any tolerably exad: method of apply- 
ing it ; and indeed before I had perfed 
faith in it ; which will not be thought ex- 
traordinary by any perfon verfed in thefe 
matters, or indeed acquainted with human 
nature in general. We always queftion 
every new fad:, or hypothecs, and more, 
fo in proportion both to its novelty, and 
importance. We are, therefore, feldom 
quite fatisfied ourfelves, till we have had an 
opportunity of fatisfying other perfons with 
refped to them. Now, it was not till the 
clofe of that year, when my experiments on 
plants were nearly brought to a conclufion, 
that I obtained that complete fatisfad:ion 
with refpe(ft to tl^is capital ufe of nitrous 


304r Ohfervations on 

air. Accordingly, it may be obferved, that 
the tefls I then made ufe of were the fame 
that I had always ufed before, viz. the 
burning of candles, and the refpiration of 
mice, in the application of which I had 
acquired a greater degree of dexterity and 
exadinefs than can well be imagined -, at 
which my friends were often much amufed, 
and myfelf, of courfe, not a little pleafed. 
On all thefe accounts, I contented myfelf 
with the more inaccurate methods of afcer- 
taining the purity of air, and made but 
little ufe of the better method, which I 
had but lately difcovered -, though I did 
not wholly negled: this method, efpe- 
cially in cafes of much confequence, as 
may be feen Vol. I. p. 90, 91, 92, &c. 

After thefe ohfervations, I think it will 
be unneceiTary to recite the particulars of 
thofe cafes in which the growth of plants 
failed. to refiiore any fpecies of noxious air. 
But, for the reafon mentioned above, it 
will be of confequence to be as particular 
as I can v/ith refped to thofe inftances in 
which it fucceeded. 


Vegetation^ 305 

(On the 28th May I introduced a flioot of 
^- ftrawberry plant into a jar containing 
air vitiated partly by the burning of 
candles, and partly by other means,- -till 
one meafure of it and one of nitrous air 
t)ccupied the fpace of 1.62 meafures; 
and on the roth of June this air was 
fo far improved, that M^hen it was- tried in 
the fame manner, the meafures of the teft 
were i .4, and a candle did not imriiediately 
go out in it. ! 

-June 29th, a quantity of air which was 
perfectly noxiousf-' riot being' in the leaft di- 
minifhed" by nitrM'S 'air" (having beeti' Jfit'ft 
injured by the burning of- candles,' ahd'kfter^ 
wards by plants confinfed, and perhaps |)u- 
trefyi-hg in i*t)', on ^he 23d of the iame 
month, '"^W^s fo far reftbred by a'^ftrawberry 
fhoat, that biie rrieafiire of it and* anather of 
nitrous air occupied the fpace of iV62mea- 
Hires/''- ^ '-■..■• ■ s. hmu: .■ 

At the fame tlinfe another quantity of air 

which had been quite noxiou^y'^and in 

v/hich a fprig of 'Winter fav-ory had growii 

X the 

306 Obfervations on 

the fame time, was fo far mftored, that 
equal meafures of this and nitrous, air: ocr 
cupied the fpace of 1.64 meafures. - -; 

July I ft, the air of a jar: in which a 
candle had burned out, and in which a 
ftrawberry ilioot had grown from the 2:3d 
of June, was fo much improved, that the 
equal meafures above-mentioned occupied 
the fpace of 1.24 meafures ^ when thofe 
in which the common air of the garden 
was ufed were 1.3. 

July 5th, air which had been fa noxious, 
that the meafures of the teft were f^^^* 
on the iirft of the fa^€ month> and in 
which a ftrawberry ihoot had grqvjr^jin 
the mean time, were 1.56. ; ^f 

At the fame time air in which a candle 
had burned out (by which I found air was 
{o far injured that equal meafures of i,i;^^.and 
of nitrous air occupied the fpace of 1.44 
meafures) and in which a very fmall fprig 
of parlley, in proportion to the fize of the 
vefTel, had grown from the iirft of the fame 
month, was fo far reftored, that when it 


Vegetation, ^07 

was examined, the meafures of the teft 
were 1.29. Alfo, ,in another quantity of 
the fame air, in which a flrawberry fhoot 
had grown the fame time, the meafures 
were 1.34 

In all thefe inflances, it will be obferved, 
that plants grew in the common foil of 
the garden. I had but one instance of any 
melioration of air in other circumllances, 
and that was not confiderable. 

July 6th, one meafure of air iw which a 
candle had burned out, and in which a young 
bean had afterwards grown feven days, and 
another meafure of nitrous air, occupied the 
I fpace of 1.385 meafures; when with the 
common air, and the fame nitrous air 
the meafures were 1.275. With air in 
which a candle had burned out, the ufual 
meafures of the teft were, as I have obferved 
before, 1.44. In all the other cafes of beans 
growing in confined air, the air was 
either made worfe, or at leaft not mended. 

All the cafes in which common air was 

improved by vegetation were thofe in which 

the roots of the plant were in the ground, 

X 2 and 

308 Obfervations on 

and flexible fprigs from them were bent, 
and made to pafs through a body of water 
into the jars or phials containing the air. 
But there was this advantage in this cafe, 
that I had no occafion to draw the whole 
fprig through the water, but only to place 
the inverted jar over it, pouring water 
into the bafon in which the jar was placed, 
in order to cut off the communication 
with the external air. But that this method 
did make an effedlual feparation between the 
air within the jar and the external air, was 
fufficiently evident from the refult of thofe 
experiments, in which the air within the 
jar was better than the common air^ and 
therefore the fame method may be depended 
upon in the preceding experiments. 

■The firfl inftance that looked like the 
lij'iplio ration of common air by vegetation oc- 
curred the 1 6 th of June, when I examined 
the air in v/hich two different flioots of 
flfawberry-plants had grown from the nth 
of the fame month. Though thefe plants 
had grown very poorly, and the leaves were 
not fenlibly expanded, the air, I obferved, 


Tiephlogljticated Air . 309 

'vyas rather better than worfe, though not 
fo much fo, as tjiat I could be quite fure 
of the fad:, But the ne:?ct day I obferved 
that the air in another jar, in the fame 
circumftances with the former, was cer- 
tainly rather better than common air; 
though iljll I fhould not have drawn any 
general conclulion from it, if it had not 
been confirmed by other more deciiive ob- 

On the 2ift of June I had, however, 
indifputable evidence of the melioration of 
air in which a plant had grown. It was a 
fprig of winter favor y, and it had grown in 
the jar from the i6th of the farne month. 
The improvement of this air, meafured in 
the ufual manner, was in the proportion of 
1.2,75 ^^ ^'ZIS- ^ ^^^ air enough for three 
trials of it, and the refvilt was the fame in 
them all. 

June 26th, common air in which a fprig 
of parfley had grown very well fi'om the 
1 6th was fo pure, that one meafure of it 
and one of nitrous air occupied the fpace 
pf 1. 1 4 meafures ; when equal meafures 
X 3 of 

3,10 Obfervations on 

of the beft common air and the fame nitrous 
air meafured, at the fame time, 1.29. I 
immediately replaced the fprig in the fame 
air, and on the 6th of July I examined 
it again, when the air was ftill rnore 
improved 5 the meafures of the teft being 
exadly i . This refult was very clear, and 
certainly remarkable. 

June 29th, a jar of common air in which 
the fhoot of a ftrawberry plant had grown 
from the 17th of the fame month, was fo 
pure, that the meafures of the teft were 
1 . 1 8 ; when, with the common air, at the 
fame time, they were 1.3. Alfo, on the 
fame day, the common air in which a fprig 
of winter favory had grown the fame time 
was improved in the fame proportion. But 
in this jar there was a little of that green 
matter, which, as will be feen hereafter, 
-ufually attends the fpontaneous produdlion 
of the pureft air. 

When thefe obfervations are well con- 
fidered, I think it will hardly be doubted, 
but that there is fomething in the procefs of 
vegetation, or at leaft fomething ufually 


Vegetation, 5 1 1 

attending it, that tends to meliorate the 
air in which it is carried on, whatever be 
the proximate caufe of this efFed, whether 
it be the plants imbibing the phlogillic 
matter, as part of their nouriihment, or 
whether the phlogifton unites with the 
vapour that is continually exhaled from 
them; though, of the two opinions, I 
ihould incline to the former. 

The aftion of a plant eonfidered as fim- 
ply vegetating in air is a thing quite different 
from the eifed that the exhalation of the 
jiower, and perhaps other particular parts 
of the plant, may have upon it. Smell, 
the old chemifts faid, was an indication of 
phlogifton, and I find that the moft deli- 
cate flowers injure the air much more than 
I had imagined. Nothing is fweeter than 
a rofe, and yet the fragrant effluvia of it is 
far from being favourable to the air in 
which it is confined. 

On the 25th of June I confined a full 

blown red rofe in about four ounce mea- 

fures of common air, having covered it 

with a fmail glafs jar ftanding in water; 

X 4 and 

312 Obfervatlons on 

and I obferved that, the next day, the air 
was fo much injured, that one meafure of 
it and another of nitrous air occupied the 
Ipace of 1.75 meafures; fo that I doubt 
not that any animal would have expired 
immediately on being put into it. The 
day following the meafures of the teft were 
1.9, and the day after fomething more. 
Notwithflanding this, when the rofe was 
withdrawn, it did not feem to have loft 
any thing of its agreeable fragrance^ 

S E C-, 

Vegetation, ©ij 


Of the State of Air confned in the Blad- 
ders of Sea Weed, 

1WAS much confirmed in the hypothecs 
of vegetation reftoring atmofpherical air 
to a ftate of greater purity, hy finding the 
air within the bladders of the common 
fea weed to be confiderably better than the 
common external air. This was a cafual 
and unexpedted obfervation that I made in 
the courfe of the laft fummer at Lymington^ 
and I wilh that fome philofophical perfons 
who live near the fea would examine this 
circumftance a little farther, both for the 
fake of inveftigating the origin of this air, 
and the particular oeconomy of the plant 
that contains it. It might even lead tq 
fome farther knowledge of the flrufture of 
plants in general. 

Before I recite thefe obfervations, I would 
remind my reader, that I formerly gave 
fome attention to the air contained in the 


314 Ohfervafions 6n 

hollow parts of certain plants, particularly 
the bladder fenay and the ftalks of onions ; 
but, in thofe two cafes, I found the air, 
as far as I could then judge, not to differ 
from .that of the furrounding atmofphere. 
This being an obfervation of no confe- 
quence, I defifted from profecuting it, ima- 
gining there muft be fome eafy communi- 
cation between thofe cavities in plants and 
the external air, fo that much difference 
Gould not be expected. I found, however, 
in the courfe of this fummer, that, in 
two other cafes, air fo confined was much 
inferior in purity to that of common air. 

Air preffed out of the ftalks of the com- 
mon jlag (as I think it is called) growing 
in water, was in fuch a ftate, that one 
meafure of it and one of nitrous air occu- 
pied the fpace of 1.5 meafures. And air 
in the infide of a plant refembling hem- 
lock was e-ven worfe than this. For when 
I examined it I found the meafures of the 
teff to be r.75. 

Upon this I was rather inclined to fup- 

pofe, that i€ the ak within the cavities of 

4 plants 

Fe get at ion, 31^^ 

plants was examined with rigour, it would 
always be found rather worfe than the air 
in the furrounding atmofphere, efpecially 
if the plant was in the fmalleft degree un- 
healthy ; as the phlogiflon difcharged in 
any tendency to difeafe would eaiily affedt 
the air of fuch cavities -, and there being 
no vifible circulation, it would probably 
retain fuch a taint a conliderable time. 
Though I might have fuppofed, that if the 
plant was very healthy, and did imbibe 
phlogiflon from the neighbouring air, the 
air in thofe cavities (in what manner foever 
it came there) would be depurated by that 
means, and thereby approach to the ftate of 
dephlogifticated air. This may perhaps be 
the cafe with the air in the bladders of fea 
weed, though I could wifh to know a little 
more concerning the origin of this air. 
For as fome of the plants grow intirely 
under water, there is no appearance of this 
air having ever been atmofpherical air, 
but rather of its being generated within the 
plant itfelf. 

I ob- 

^i6 Ohfervattons on 

I obferved three kinds of this fea Weed» 
one which I take to be the quercus marinus, 
the bladders, when full grown, being about 
half an inch in diameter, and rather of an 
oval form -, another in which the bladders 
were fpherical, about a quarter of an inch 
in diameter; and a third in which the 
bladders were much larger than thefe, being 
formed by the feparation of two lamincB of 
which the plant conlifts, fo as to refemble 
a fillet, the bladder being exadly of the 
hreadth of the flag, and rather longer than 
it is broad. 

The firft of thefe was moil common on 
the fea fhore at Lymington. The firft that 
I took up had lain a confiderable time on 
the {hore, fo that the bladders were become 
Very hard and brittle, and the air within 
them was exadtly in the fame ftate with the 
air of the atrnofphere. But afterwards, on 
the 25th of July, I happened to meet with 
a quantity of this weed that had juft been 
thrown up by the fea, quite moift, and the 
bladders foft. Burfting them under water, 
^nd examining the air, I found that one 


Vegetation, ^x^ 

meafure of it . and one of nitrous air occu- 
pied the fpace of not more than one mea- 
fure; whereas, when I applied the fame 
teft to the common air, the meafures were 

This degree of purity fo far exceeded my 
expectations, that, though I made the ex- 
periment with all the attention that I was 
capable of, I could not help fufpedting that 
I had, unperceived by myfelf, let fome of 
the air efcape as I was mixing it^ and I ac- 
quiefced in this idea fome time, in confe- 
quence of having found the air within 
fome of the largeft of the bladders above- 
mentioned, even when plucked up from 
the roots with my own hands no 
better than common air. But many of 
thefe bladders were old, and quite black, 
growing upon a beach where they were not 
intirely covered by the fea, even at high 
watery fo that the bladders not beinp- aK 
ways moiil, there might have been fome 
communication with the external air ; and 
the infide of fuch bladders, if they ihould 
happen to be in a ftate of decay, would 
2 ' greatly 

3i8 Obfervations on 

greatly contaminate and deprave the air 

contained in them. 

On the 29th of July, I gathered a quan- 
tity of this weed containing the largeft 
bladders, and alfo of that which had the 
fmalleft. At that time the air in thefe did 
not differ from the common air. Of the 
large bladders I feparated the black ones 
from the reft -, and, preffing out the air 
contained in them, I found that one mea- 
fure of it and one of nitrous air occupied 
the fpace of 1.2 meafures; but with the 
air from thofe bladders which were not 
turned black, the meafures were 1.06. 

Thefe obfervations were ftill in fayour of 
the greater purity of the air contained in 
thefe bladders ; but I was thrown back 
into my former doubts, by finding, pre- 
fently after, the air in the bladders of fome 
weed that I took up quite freih and moift 
on the fea (hore, did not differ at all from 
the common air. * Had I happened to have 


)— *■!■■■ ■■ ■ -I — ■■■■■»■'■■*■■— — I ■ I -^ — ■ 1 ■■■—■—I— I II K"^' 

* I might have confidered that, though thefe weeds were 
mo'iji^ in confequence of having been lately thrown up by 
the fea, it might have been a long time fmce they were 
in a ftate of vegetation. 

Vegetation, ^i^ 

met with this weed at the firft, I (hould 
certainly have examined into the matter no 
farther ; but having had different refults in 
my former trials, I was not willing to leave 
the fea with my doubts unfatisiied; and 
for this purpofe I went to the fea fhore at 
low water, and gathered the plants that 
were then growing in the water -, fo that 
they could never have been dry ; and the 
air within the bladders could never have 
had any communication with that of the 
atmofphere. I gathered thofe plants only 
that were feemingly young and frefh ; and 
I took a great quantity of them, fo as to 
have air enough for many experiments -, and 
being determined to abide by the refult of 
this trials I proceeded to the examination of 
it with the greatefk precaution ; when I 
found, in three different trials, that oner 
meafure of this air and one of nitrous air 
occupied the fpace of i.i meafures. At the 
fame time, with the fame mixtures of com- 
mon air, the meafures were 1.35. 

I could have wifhed to have examined 
the air of thefe weeds from the firfl formar 


320 Ohfewations ofi 

tion of the bladders and at different tiinef 
of the year, &c. butlmuft lea\^e~this to be 
farther invefligated by thofe who hav^ 
better opportunities for the purpofe* 


Of the Property of the Willow Plant to ah* 
forb Air, 

F the various plants on which . I mad^ 
experiments iii the courfe of this 
fumnier, I met with one which had the re- 
markable quality of abforbing a great pro*» 
portion of any kind of air to which I ex^ 
pofed it. It is the epilobium hirfutufn d£ 
LinntEus, in Englifli the willow plant, and it 
grows beft in the water of marjfhy ground. 
The method in which I rriade the experi- 
ments was by fixing the jar of air with its. 
mouth in the water in which the plant 
grew, keeping it upright, by faftening it to 
a ftick fixed in the bottom of the pool, 
then bending the plant under the water, 


Vegetation. 3^1 

«nd introducing th'e top of it into' the ia^ 
fide of the j at. 

I prefently f6und that the common air to 
which it was expofed in this' manner was 
leonfiderahly diminifhed, and rendered 
ii<bxit)us ; btit h^V^ing neglected one of thefd 
jkfs for ahout a- week j I was furprized tcJ 
iiM that neai* ane half of the whole quarir-^ 
Hit^ of a^r was^ abforbed, the water having 
ftferi fo' fai" within the jar*- whereas, iri 
general, the diminution of aft* bccafioned 
fey whal^ I fu|i>po3[e to he mei'e phlogiftoh, 
a^ fri'thie procefs of iron filings and brim^ 
ftone, or the calcina-tion of metals, '&c. dbe$ 
lilbt' exceed one' fourth of the wholes Sup- 
pofing, however, tliat I might not h^ve 
taken fufficient not!ice of the quantity o# 
air originally contained in the jar, I fe^ 
plated the experiment in avjar about ten 
l-nches Ibrig, and one M' diamet^ry arid 
fo\!itid, after fbnie time, that the diteiri\i« 
tibii Went unqueftiohably beyond ahe foiirth 
of the whole J and thehj to profeciute the 
the experiment farther, I iiitVoduxied other 
plartts of this kind into jars about nine 

Y inches 

322 Qhfervat0ft5 on 

inches in length, and 2^ in diameter, one 
of them filled with inflammable, and th« 
other with nitrous air. 

.After about a fortnight, I noted the flatc 
6f thefe. plants, and of the air to which 
they were expofed, and found them to be as 
follows : The; plant which had been expofecj 
to common air, in the jar about ten inches 
long and one inch wide, and which had 
been,. in all, about a month in that fituation, 
had abforbed feven eighths of the air in the 
jar. The plant was quite yellow and dead ^ 
but though it had been fo for forne time, ife 
had flill continued toabforhthe air. . . . 
. The plant which had been confined only 
about a fortnight, in one of the larger jars 
of common air, was quite green, and had 
confumed three fourths of it. 

The plant in a jar of the feme fize, con- 
taining inflammable air, had confumed one 
third of it, and part of the remaindcF 
(which I drew from it) was, to all ap- 
pearance, as inflammable as ever it had been* 
The plant was green. 

• The 

Vegetdtion. 323 

The plant in the nitrous air was yellow 
and dead, and had confumed one third of 
its air. 

-In this ftate I was obliged to leave thefe 
plants, and to fufpend all my other experi- 
ments on plants by my journey to the fea 
iide ; but I had accounts fent me of the 
ilate of them from time to time, by which 
it appeared, that the air continued to di- 
minifh till the common air in the narrow 
jar was only one tenth of its original quan- 
tity, the inflammable air was reduced to 
one feventh of the whole ; and the air in. 
the other jars was diminifhed in about the 
fame proportion. But at length, the fum- 
mer being very dry, the water failed, and 
the common air, of courfe, got into the 
jars. I regret, particularly, that I had no 
opportunity of examining the ftate of the 
injiammable air in the laft ftage of its dimi^ 

Finding this plant to abforb fo much air, 

I was defirous of knowing what became of 

it, whether it was incorporated in the fub- 

ftance of the plant, or was merely ftrained 

Y 2 through 

3^4 OhfervatwU on 

through ft*' V For this purpofe I put ttlie 
rdot'oF orte of th^ plants, with all the 
earth that adhered to it, into a jar ; and 
bending the plant a littk, placed the jaf in 
fueb a manner, as that the mouth of it was 
jufli iftimerfed in a p^U of vrater, and the 
piarit> ttoHgh m. an auk ward fituation> 
grew ptett-y well; the upper part berng 
fupported; and alfo turning upwar-<$s- of it*^ 
felf, h^ its natural growth. 

Sbnfsd air was certaiiily ftrained fhrotrgh 
this plant f but m^thr 1-els than 1 had ex- 
pe<fted, conildering iha q^uantitjr thdt I 
fuppofed it would have abforbed ifi- the 
fame tinier, aft laafi if \X had grown- freely irs 
itb aat^ral lituation. The air which I 
coIlfe6ted irf this manner was almbft intirely 
J)hlogiiiicatedy as W^s' always that which 
remained of thd conimdfi 'iit that tk^ pilant 
had ab for bed. 

To try whether the plant would adlually 
abforb air in the iituation above defcribed, 
when the root was coniined in- a jar oi 
water, I gave it another bend near the top,- 
s^ad.' placed a jar^ of common air over it, 


Vegetation. 325 

^^aiiding in another velTel of w^tejr; tiut 
$kx^ plant would aot bear fp much torture, 
^d though it did jiot die immediately, it 
decayed gradually, and the experiment had 
no effed:. 

It will certainly be well worth while to 
compare all the circumftances in which 
air is abforhed, as well as thofe in which 
|t is merely diminijhed to a certain degree, 
in order to afcertain the circumflances that 
are pommon to all the cafes, and diereby 
difcover the proper caufe of this remarka- 
ble phenomenon. Water, and many other 
fluids, have this property in fome degree, 
as has long been known to natural phild- 
fophers, who did not give much attention to 
ithe quality, or chemical properties of air. 
I difcoyered it in a ilill greater degree in oil 
cf turpentine. See Vol. III. p. 92; and 
that excellent philofoper the Abbe Fontana 
Jias difcoyered it in a much greater -degree 
AiU in charcoal. This plant, however, 
feems to poflefs the fame property in as 
great a degree as charcoal. It only requires 
more time to produce its effed:. At another 
Y 3 opportunity 

326 Obfervations on 

opportunity I propofe to examine this mat- 
ter a little farther. At prefent, no con- 
jedure occurs to me that I think worth 
communicating to the public. 


Of the Growth of Plants in Dephiogijil- 
cated Air, compared with their Growth 
in other Kinds of Air, 


T will be allowed to be an argument 
favourable to the hypothecs of vegeta- 
tion repairing the injury done to the air by 
refpiration and putrejfadion, that plants do 
not grow fo well in dephlogiflicated air, as 
in common air. Of this I had fome fufpi- 
cion from the iingle experiment, the refult 
of which is recited in my third volume 
p. 335.5 but I am now pretty well fatisiied 
with refpedto it, from experiments begun 
in April 1777, and continued occalionally 
in the courfe of the fummer following, 

■ In 

-. Vegetation. 327 

In order to compare the vegetation of 
plants in air differing as much as poffible. 
with refped: to phlogiflon, I took three 
iprigs of mint -, and having put all their 
roots into phials containing the fame pump- 
water, that had been fome time expofed to 
the open air, I introduced one of them into 
a jar of common air, another into one of de- 
phlogiilicated air^ and the third into air that 
|iad been phlogifticated with nitrous air fe^ 
yeral months before. It was in fuch a ftate, 
that one meafure of it and one of nitrous air 
occupied the fpace of 1.75 meafures. This 
was done in April; and examining the 
plants on the 12th of May following, I 
found that the plant in this phlogifticated 
air had grown remarkably well, much bet-i. 
ter than that in the common air j whereas 
the plant in the dephlogifticated air had a 
very lickly appearance. 

I examined thefe plants on the z6th of 
the fame month, when the appearances 
continued nearly the fame^ And thefi, 
examining the ftate of the air, I found 
that, though the plant in phlogifticated 
Y 4 air 

^aB Obfervations on 

air had grown fo well, the air was not fen- 
iibly improved by it. The dephlogifticate(J, 
air was injured, which I attributed to th^ 
rotting of fome of the leaves of the pi^nt. 
The common air I did not attend to. ' 

On the 7th of June following, I took 
an account of three fprigs of mint, which 
had been growing, I believe, fome weeks 
in dephlogifticated air, and of three other;?, 
which had been growing the fame time, 
and in all the fame circumflances in other. 
refped:s in common air -, and obferved that, 
in all the three cafes, the appearances were 
■deciiively in favour of the plants in the 
common air, the ihoots being twice as 
large, and every other appearance of health 
in the fame proportion. 

I do not fay that even thefe obfervations 
are quite fufficient to determine the quef- 
tion 5 but they feem to make it probable, 
that dephlogiflicated air does not fupply 
that pabulam v/hich plants derive even 
from common air; though I own it may 
injure them on fome other account. Even 
Mr. Scheele, who maintains that vegetation 
Z has 

vie get at ion, 3^ 

Jias die fame effe(9: on ^ir that refpiratioa 
li^y I find, j^Uows that plants do not 
grow fo well If), dephlogifticated ,as in co pi 
mon air. 


Of the Growth of Platits with their Leavesi 
in fixed Air, mid their Roots in Water 
impregnated with fixed Air, 

WHILE I was attending to the Gomr- 
parifon of the growth of plants in de- 
phlogiHicated and common air, I at the fame 
time made a few farther experiments on the 
growth of plants with their leaves expofed 
to fixed air, though I was pretty well fatif- 
fied, from the experiments recited Vol. III. 
p. 303, &c. that this kind of air is undoubt- 
edly injurious to plants growing in it. I 
wi filed alfo, once more, to try the elFed of 
inflammable air with refped: to vegetatioa. 
Accordingly, in the fame month of April 
^777, I introduced afprig of mant into a 
of air one third fixed and the reft 

Common ; 

33'0 Ohfervations on 

common ', and having only once Aipplkdit 
with freih fixed air (when the bulk of the 
former was abforbed by the water) I obferv- 
ed, that on the 3d of May following, there 
were black fpecks on feveral of its leaves, 
and in the courfe of a week it was almoft 
wholly black, and evidently d^d. It had 
pot grown at all. 

At the fame time I had put another fir 
milar plant into a jar of half frefh made in- 
flammable air and half common air, but it 
died prefently. I found, however, by 
fubfequent trials, that plants would bear a 
greater proportion of inflammable than 
they would of fixed air 3 fo that from the 
circumflance of plants merely li'ving in a 
proportion of fixed air, it cannot be in- 
ferred that it is ^ ^iJW^ ^^ all favourable 
to their growth. 

The few experiments that I had an oppor- 
tunity of making, at the time of my lafl pub- 
lication, left me altogether undecided with 
refpedl to the efFecl of water impregnated 
with fixed air on the roots of plants. $ec 
Vol. ill. p. 320, 6cc. But the many expe- 


Fe get at ion. .331 

riments that I have made fince, in 1777, 
and 1778, have not left a fhadow of doubt 
on my mind, that fuch water is hurtful, and 
finally fatal to the plaijts growing in it, at 
leaft to fprigs of mint -, for I did not make 
the trial with any other plants. 

Gn the 28th of May I placed, in a green 
houfe, and not in my laboratory, as in the 
experiments mentioned in my third volume, 
three iprigs of mint, with their roots in 
phials of water impregnated with fixed air, 
and three other plants of the fame kind with 
their roots in the fame water unimpregnated. 
After a week I changed the impregnated 
water, on account of the mouths of the 
phials being left open, left the plants fhould 
have been injured .by putting any thing 
about them, to prevent the efcape of the air 
from the water. 

During tv/o or three days at the firfi:, the 
plants in the impregnated water were more 
vigorous than the others -, but on the 8th of 
June following, they all looked much worfe 
than thofe in the common water. Alfo 
thofe in the common water had long white 


.^3,2 Ohfervatlofts on 

lilameijtsiliootingfrom their roots, whereas 
tJhiofe in the impregnated water had none of 
them. On the i8th of June^ the plants in 
the impregnated water were all quite dead, 
their leaves having all fallen off one after 
another, beginning at the bottom. Exa- 
tnining one of the phials, I foupd that it 
jContained between one fifth and one fixth 
of its bulk of fixed air. 

I repeated thefe experiments feveral tinves 
in the courfe of that fummer, generally 
ufing many more plants than in thefe laft 
mentioned, but the refult was the fame ia 
them all. However, as it generally happen- 
ed, on what account I cannot tell, that the 
plants in the unimpregnated water died, 
though later than the others, I deferred the 
lail and decifive trial till the year following, 
after which I had no doubt remaining on 
the fubjed. 

On the 4th of May 1778, I put feyen 
fprigs of mint into pump water impregnate4 
with fixed air, and ten or twelve in the 
fame water unimpregnated, the phials being 
fimjlajr, jari(J ,1 placed theni all in a fummer 


Tegetation. ^.^^ 

houfe, ill the fame expofure. I renewed 
the impregnated water every week, till the 
23d of June, when all the plants in the wa- 
ter impregnated with fixed air were dead, 
the roots being black and rotten i while 
the other plants were in as flourifhing a ftatc 
as pofiible, and continued to flourifh long 
after, till I difcharged the experiment. 

On. this occafion I did not obferve that th^ 
plants in the impregnated water were at any 
time more flourifhing than the others, not 
even at the beginning -, and after -a fortnight 
the difference in appearance, to the difad- 
vantage of thofe in the impregnated water, 
, was very vifible. Thofe w^hich grew in the 
common water threw out many white fila- 
mients from their roots, many of tliem fo 
long as quite to fill the phial, twilling them- 
selves in all directions, and exhibiting avery 
beautiful appearance j whereas there wm 
Jaothing of this kind in any of the phials of 
impregnated water. On the contrary, the 
roots became prefently black, and at.length 
rotted quite away. 


334 Obfirvations on 

One of thefe I had overlooked, and had 
neglected to change the water ; and this 
plant threw out a few white filaments -, but, 
on renewing the impregnated water, they 
prefently became black and perifhed. 

It was remarkable alfo, that two of the 
plants in the impregnated water threw out 
thick knots of thofe white filaments in the 
necks of the phials, juft above the furface 
of the water, but not one of them within 
the water itfelf, or ever entered the water. 
Alfo, when I took one of thefe plants, the 
roots of which were quite perifhed, out of 
the impregnated water, and put it into a 
phial of common water, it threw out new 
white roots above the place that was de- 
cayed, and after\^^rds grew very well. 

Mr. Hey happened to fee thefe plants in 
the laffc ftage of the procefs, and thought 
no experiment could be more fatisfadory. 



A;r emitted from Water. ^^ 5. 


Of the fpontaneous 'EmiJJion of dephjogijii-^ 
cated Air from Water in certain Circum-^ 


FE W perfons, I believe, have met with 
fo much unexpe(5led good fuccefs as 
myfelf in the courfe of my philofophical 
purfuits. My narrative vi^ill fhow that the 
firfl hints, at leaft, of almofl; every thing 
that I have difcovered, of much import- 
ance, have occurred to me in this manner. 
In looking for one thing I have generally, 
found another, and fometimes a thing of 
much more value than that which I was 
\vi queft of. But none of thefe unexpected 
difcoveries appear to me to have been fo 
extraordinary as that which I am about. to 
r-elatCi and it may ferve to admonifh all 
perfons who are engaged in fimilar pur« 
fuits, not to overlook any circumftance re- 
lating to an experiment ; but to keep their- 
eyes open to every new appearance, and to^ 

|;J.6 Ohfer'uations &H 

give due attention to it, how inconfideraMc 

Ibever it may feem. 

In the courfe of my experiments on th^ 
growth of plants in water impregnated with 
fixed air, I obferved that bubbles of air 
feemed to ilTue fpontaneoully from the 
flalks and roots of feVeral 6£ thofe which 
g|.*ew m the unimpregnated water; and'-| 
imagined that this air had percolated through 
Ifhe plant. It immediately, occurred to n>e^ 
that if ' this .viras the cafe> the ftate qf thatr 
air niight pofHbly help to determine tvh^^ 
I was at that time invefliigating, viz, whe^' 
ther the growth of plants contributes to 
purify, or to contarninate the air. For if 
this air fhould prove to be better than com-^ 
mon air, I thought it would ihow, that the 
phlogifton of the imbibed air had been re* 
tained in the plant, and had contributed t6 
tiue nourifliment of it, while that part of 
the air which paffed through the plant, 
having depolited its phlogifton, had been; 
rendered purer by that means ; though if 
the air fliould not have been found better 
than conimon air, I fliould not have con- 

Air emitted hy Water. 337 

eluded my hypothelis was falfe ; fince 
plants, like animals, might take in phlo- 
gifton in one ilate, and emit it in another. 

With this view, however, I plunged 
many phials, containing fprigs of mint in 
water, laying them in fuch a manner, as 
that any air which might be difcharged 
from the roots would be retained in the 
phials, the bottoms being a little elevated. 
In this pofition the fprigs of mint grevy 
very well, and in fome of the phials I ob- 
ferved a quantity of air to be colle<5led, 
though very flowly j but I was much dif- 
appointed in finding that fome of the mofl 
vigorous plants produced no air at all. At 
length, however, from about ten plants, I 
colled:ed, > in the courfe of a week, about 
half an ounce meafure of air. This was 
the 19th of June 1778; and, examining it 
with the greatefl care, I found it fo pure, 
that one meafure of it and one of nitrous 
air occupied the fpace of only one meafure. 

This remarkable fa<5t contributed not a 
little to confirm my faith in the hypothefis 
of the purification of the atmofphere by ve- 
getation i but I did not enjoy this fatisfac- 

Z tion 

5^'S ObJh^dtiQns on 

tion long, ikor I confidered that, if tliiff 
was the proper effed: of vegetation, it fiiufl 
be univerfal, and could not be confined t<i it 
few plants, efpecially when others of the 
fame ijpecles produced no fuch effed^. Be- 
iides, when I removed the air-producing 
plants, as I thought them to be, into 
other arid cleaner phials, I found that they 
yielded no more air than the other plants 
had done. And, what I thought more ex- 
traordinary ftill, the phials in which thefe 
plants had grown, the infides of which 
were covered with a green kind of matter, 
continued to yield air as well when the 
plants were out of them, as they had done 
before. This convinced me that the plants 
had not, as I had imagined, contributed 
5ny thing to the production of this pure air. 
About the fame time I obferved that great 
plenty of air rofe Ipontaneouily from the 
bottom and fides of a tall conical receiver, 
about eighteen inches high, and five wide at 
the bottom originally made for the experi- 
ment of the fountain m vacuo, but which 1 
had often ufed as a magazine for various 
kinds of air, and which was at that time em- 

Aif einltted by Water, 339 

J)k)yed for the fame purpofe ; and both the 
plate on which it ftood inverted, and the 
lower part of the receiver, w<^re covered 
with this green matter. 

To make my obfervations on this h6W 
fubje<5l of experiment with n*iore attention, 
I transferred the air it had contained into 
another vefTel, filled the receiver with frefh 
pump water, and placed it where it had ftood 
before, which was in a window^ on which 
the fun fhone -, when air bubbles prefently 
bbgan to rife very faft, fo that, in three days, 
I had colle<5ted feven ounce meafures, and 
this was fo pure, that one meafure of it, 
and two of nitrous air occupied the fpace of 
fOiir fifths of a meafure. 

Having found many of my phials which 
had the fame green matter in them, I filled 
them alfo with frefh pump water ; and, in- 
verting them, I eolledted from th«m all coii^ 
fiderablb quantities of the fame depHogifti- 
cated air, efpecially when they wefe placed 
in the fun ; and it was very arnufing to watch 
them, and to obferve the bubbles fwell, and 
Z 2 ' detach 

34® Ohfer'vattons on 

detach themfelves gradually from the green 


When I had advanced thus far in this 
interefting inquiry, I was obliged to deiift 
from the farther profecution of it, on ac- 
count of a journey, on which I was abfent 
fome months ; and all that I could do was 
to leave a number of phials filled with dif-^ 
ferent kinds of water, as river water, pump 
water, and rain water, with feveral other 
little varieties, in order to difcover the cir- 
cumflances that were moft favourable to 
the production of this green matter, what- 
ever it was. 

At my return, on the 8 th of September, 
I found no green matter in any of the phi- 
als, excepting thofe which contained pump 
water. Neither the rain water, or river 
water, had produced any. This pump 
.water contains a confiderable quantity of 
.fixed air, and I muft alfo obferve that the 
infides of the middle and lower glaffes in 
one of Mr. Parker's apparatus's for impreg- 
nating water with fixed air were almoft 
coated with this green matter. 


Air emitted by Water, 341 

After this I placed in my garden a large 
glafs jar nearly filled with pump water, which 
I had ftrongly impregnated with fixed air, 
and alfo jars of river water, rain water, and 
pump water unimpregnated ; and on the 
14th of Odlober, I found almofi: all the 
bottom of the jar which contained the im- 
pregnated water covered with the green 
matter, but there was none at all in any of 
the other jars. This makes it probable, 
that the fixed air in the water contributes 
to the produdlion of this matter. 

That the external air, or animalcules in 
it, have nothing to do in the formation of 
this green matter, is evident from feveral 
of the preceding obfervations. This could 
not be the cafe, for inftance, with the large 
inverted receiver, which had always yield-r 
ed the greatefl quantity of this airj or vvith 
the water in the middle vefTel of Mr. Par- 
ker's apparatus. Befides, at other times I 
have kept phials clofely corked, and yet 
have found the green matter at the bottom 
of them, and it has yielded air plentifully, 
cfpecially in the fun, or when placed near 
the fire. For when the matter is ; once 
Z 3 formed. 

'34-2 , utJerv^UtQns on 

formed, nothing but a certain degree of 
warmth fcems to be neceflary to its a£bu4 
prod,u(flion of air. 

The produdiion of this green rnatter in 
f lofe veiTels feem^ to prov? that it can neji- 
ther be of an animal or vegetable nature^ 
but a thing fui generis, and which oygl^t? 
therefore, to be charaderized hy forne 
peculiar nam,e ; and all the obfervations 
that I have jnade upon it with the micraf- 
cope agree with this fuppofition. For, 
excepting a few iilaments, that were hol- 
low, and two or three globular pieces, 
perforated with fome regularity, all the reft 
of the fubiliance feemed to be a co^igeries of 
matter of a compa6t earthy nature, the 
pieces feparately taken refembling bits of 

I have had fome appearances, which, 
extraordinary as it will feem, make it rathet 
probable, that light is necelfary to the for- 
mation of this fubftance ; but many more 
obfervationSy which I believe can only be 
made in the fummer feafpn, will be neceft 
•fary to determine this. On the 23d of 


Atr emitted by Water* 343 

OiStober, I obferved that two fmall phials, 
which had been filled with pump water, 
and clofely corked on the 9th of AogofI: 
preceding, had both of them a quantity 
of this green matter, while an open jar of 
the fame' water, but ia a much worfe light 
had none of it. There was, indeed, a 
greater depth of water in the jar than in 
the phials ^ and though I have generally 
obferved that this green matter is firfl 
formed at the bottom of the vefTels, it may 
ppffibly require more time to the formatioa 
of it in proportion to the depth of water. 
Two other jars, however, about an inch 
deeper than that above-mentioned, and 
quite filled with the fame water, placed 
jn the window on which the fun fhone 
had acquired this green matter, even in lefs 
time than the two fmall phials above- 

From green^ this fubftance paiTes gradu- 
ally to a kind of yellow ^ or rather orange 
colour. For on the 1 4th of Odober, I 
obferved that the large recei|irer in which 
I had at firft colleded a confiderable quan- 
Z 4 tity 

344 -. Obfervations on , 

tity of this pure air, and which I had 
always kept full of water, continued to 
yield air as copioufly as ever, though both 
on the receiver itfelf, and on the plate on 
which it ilood, the colour of this fubllance 
was quite changed to the orange colour 

On the 17th of September I had taken 
all the air from this receiver, and on the 
14th of Odlober following, on which I 
obferved its change of colour, I took from 
it about nine ounce meafures of air the 
very pureft air I had ever got in this me- 
thod* For one meafure of it and two of 
nitrous air occupied the fpace of 0,44 
which is quite as pure as dephlogiiticated 
air at a medium. 


THE preceding part of this fedion w^as 
written while I imagined that the pure air 
I have mentioned in it was yielded by the 
gree?i mattery which I have defcribed, as 
depolited from the water. But I prefently 
afterwards coniidered that the formation of 


Air emitted by Water* 34^ 

the bubbles of air at the green matter was 
no proof that they were yielded by it s fince 
no air, or even vapour, can iffue from wa- 
ter, but at the place where it is bounded 
by fome other fubilance -, and the water 
might yield its air contiguous to one kind 
of fubilance in preference to another. 
Though, therefore, I had not perceived 
any bubble of air to iffue from the water 
that had depofited it, or from any part of 
the tranfparent glafs, but only, as it feemed, 
from the green matter, I had been too hafty 
in concluding even that the water could 
not yield the air but with tshe alliftance of 
that fubflance. At length the following 
experiment gave me jufl ideas on the 

Obferving one of my phials of water 
that had got a coating of the green matter 
yielding air very copioufly, I poured the 
water out of it into a clean phial, and 
found that, by the agitation given to it 
in the adt of decanting, it fparkled as 
much as any Pyrmont or Seltzer water. 
Inverting it in a bafon of water, I col- 


2^S Objervathns on 

levied the air, and found it to be very pur^e. 
1 jtreafed feveral other phials in ^he lame 
inaxinefj and the fubfequetit appearances 
{jdng t!![iQ fame^ I had no doubt b.Ht tha,t 
when water is brought into a ftate proper 
for depofiting that green matterj it is^ by 
th^ fame procefs, prepared for the fponta- 
ueous emiffion of .a cpnliderable quantity qf 
pure air. I therefore difmiffed all farther 
attention to the green matter, and ihall 
leave it, after rnaking the following pbfer- 

I nevier fotmd it except in circumflances 
IB which the water had been expofed to 
light i ai)d when^ after ftanding in the dark, 
the water has depofited a whitifh filmy 
matter, it has become green after a few days 
cxpofure to the fun. It was moA freely de- 
pofited from my pump water, and efpecialiy 
when it had been impregnated with fixed 
air, but I have found it both in river water, 
.and rain water, ^fter longer ftanding. I have 
.generally found it at the bottom of tt^ 
vefiel, but fometjmes it has been firfl 
formed at the top, and the coating from 


Air emitted by Water. 347 

jhe bottom and that from the top meeting, 
the whole phial has acquir-ed a coating of 
it from being once filled with pump water. 

It Is poflible that, in fome futi^re timC;, 
I may examine farther into the nature of this 
matter, thus depofited from ; water. But 
upon difcovering that it was pnly a circum- 
ftance preceding the fpontaneous emiflion 
pi the air from the water, I gave attention 
1:0 the water only, and to the relation it 
jDore to the air contained in it, which is cer- 
tainly not a little extraordinary j and when 
^nveftigated farther, will, I doubt not, ap- 
pear to be a fad: of the firft confequence 
refpedting the do6:rine of the atmofphere. 

i did not get this light into the bufinefs 
|:ill it was too late in the laft fummer to 
make much ufe of funfiine, but I was a£r 
^duous enough to make all the ufe I could 
of fuch weather as we had. And the gene- 
ral conclulion I have drawn from the whole 
that I was able to obferve is, that whatever 
air is naturally contained in water, or in 
fubllances diffqlved in water, as calcareous 
iiiatter, &c> becomes, after long ilanding, 
3 httt 

34^ Ohfervations on 

but efpccially when expofed to the fun, de-^ 
pirated^ fo as at length to become abfolutely 
dephiogifticated ; and that this air being con- 
tinually emitted by all water, expofed to 
the action of the fun's rays, mull contribute 
to the melioration of the ilate of the atmo- 
fphere in general. 

When I have kept water a long time in 
the fhade, it has not generally yielded any 
other kind of air than it would have yielded 
at the firft j and, though, when it has been 
kept in an open veiTel, the air has been 
better, it has never been fo good as the air 
in the fame kind of water that has been 
expofed a much lefs time to the fun. 

No degree of warmth will fupply the 
place of the fun's light ; and though, when 
the water is once prepared by expofure to 
the fun, warmth will fuffice to expel that 
'ajrj yet, in this cafe, the air has never been 
fo pure, as that which has been yielded 
fpontaneoufly, -without additional heat. The 
reafon of this may be that, befides the air 
already depuratdd, and on that account 
ready to -quit its union with the water, 


' Air emitted by Water, 34^ 

heat expels, together with it, the air that 
was phlogifticated, and held in a clofer 
union with the water ^ which air the a(3:ion 
of light, whatever that be, would in time 
have depurated alfo. 

The quantity of air yielded by water 
' Ipontaneoufly far exceeds that which can be 
expelled from it by heat. Indeed I have 
frequently obferved that whatever circum- 
ftance depraves air, lelTens alfo the quantity 
of it 5 fince it requires a large quantity of 
dephlogillicated air to make a fmall quan- 
tity of phlogifticated air, or even common 
air, which is air partially phlogifticated. 

If the water naturally contains fixed air, 
yet in confequence of this expofure to the 
light it is all diffipated, and the natural re- 
liduum of it becomes pure dephlogiflicated 
air. For no fixed air at all, but only the 
pureft dephlogiflicated air, is at length pro- 
cured from it ', and water impregnated with 
fixed air yields, after this expofure, the 
greateft quantity of dephlogiflicated air. 

I fhall not recite the particular experi- * 
ments that have led me to thefe conclu- 

fions ; 

^^o Obfef"Ddtt6ns on 

iions j partly becaufe they are too numerous, 
and alfo becaufe I hope to repeat them to 
more advantage in a more favourable feafoA 
of the year; but I fhall feled a fev^r, which 
fufficiently eftablifh every thing that is of 
importance in thefe conclulions. 

The large receiver of which I have mad« 
mention, as having ferved me for a maga- 
zine of air, and which I find contains 135 
ounces of wdter, I have already obferved 
yielded, when filled with pump water, 
nine ounce meafures of very plire dephlo- 
giflicated air, after being expofed to ths 
iun from the 17th of September to th^ 
14th of Odober. I then filled 'it ^ith 
frefh pump water, and placed it in my la- 
boratory till the 8 th of December (with 
its mouth inverted, as before, in a difh of, 
the fame water) and in all this time not a 
finglc bubble of air came from it. But oii 
being placed in a fouth window it immedi- 
ately began to yield air, and continued fo 
to do whenever the fun llione, till the 
2jfl: of January following, when there 
might be about four ounce meafures of air. 

I then 

Air emitted iy Wafer. ^^t 

I then placed the receiver, and the difh ia 
which it flood, in a large pan of water,- 
which I made to boil, and kept boiling the 
whole day, till no more air could be dis- 
charged from it ; and the next iiiorning, 
ivhen it was cold, I examined the air, and 
found it fo be in all fix ounce meafures. 
No part of it was fixed air, and one mea- 
fure of it and two of nitrous air occupieli 
the fpace of .9 meafures ; whereas, 'v^ith 
the air produced fpontaneoufly, in ih^ 
light of the fun, the fame meafures wer4 
.44, and the quantity nine ounce nieafures, 

BelideS, I am by no means certain that» 
in the former cafe,' the water had yielded 
all the air that it would have done. For at 
that time I irriagi'ned it was the green matter 
tliat yielded the air, and therefore thought 
it* to be of no confequence, with refped: to 
wiiat I then had in view, v^hether I got 
little or more of it. 

Having, by the preceding experiments,, 
afcertained, iii fo'me meafure, the quantity 
arid quality of the air yielded by this wa^ 
ter, both wholly, and alfo in part fponta- 


^^2 Obfervatlons on 

neoully, I filled the fame receiver with the 
pump water; and, without expofing it to 
the light at all, put it into the pan of wa- 
ter, and found that, after keeping it boiling 
all day, I got no more than li- ounce mea- 
fures of air from it*. Examining it the next 
morning, no part of it was fixed air, and 
one meafure of it and one of nitrous air 
occupied the fpace of 1.26 meafures; when, 
with the common air, the meafures of the 
teft were 1.3 j fo that it was a little better 
than common air. 

When I again expelled air from the fame 
pump water, and examined it immediately, 
I found a part of it to be fixed air ; but I 
am confident not fo great a proportion of 
it as I had fometlmes before found in the 
fame pump water. It may, therefore, be 
worth while to examine the air from the 
fame water at different times of the year, 
and in other different circumftances. 

In my former publication. Vol. Ill, 
p. 267, I have obferved that when water 
has been made to imbibe inflammable, or 
nitrous air, the air that is immediately 


Vegetation. 3^3 

afterwards expelled from it is alfo inflam- 
mable or nitrous ; though whether they were 
fo in exadlly the fame degree I cannot pre- 
tend to fay. However, now, on obferv- 
ing the operation of water on the air con- 
tained in it, and retained a coniiderable 
time, I boiled a quantity of water, and then 
made one portion of it imbibe common 
air, another phlogifticated air, and a third 
dephlogiflicated air. In this fituation they 
remained near a fortnight, but not expofed 
to much light 5 when the common air that 
was not abforbed by the water I found to 
be conliderably phlogifticated, which agrees 
with my former obfervation on the fub- 
je6l ; and the air expelled from the water 
was much purer than the common air. 
For one meafure of it and on^ of nitrous 
air occupied the fpace of one meafure. 
The dephlogiflicated air alfo came out of 
the water a little improved; but the phlo- 
gifticated air was not fenlibly mended. 

Had thef® kinds of air continued longer 

in the water, and been expofed to the light 

of the fun, it is probable that the com- 

A a mon 

354 Ohfervations on 

mon aiv would have been ftill more pure, 
and alfo that even the phlogifticated air 
would have been mended. I fhall not fail 
to make a full trial of this whenever I re- 
fume the experiments. 

Till thefe lafl experiments on air in water, 
I had concluded that the air naturally con- 
tained in water iq alv/ays mixed with fixed 
air, and worfe than common air 5 and I had 
not at all confidered the alteration that length 
of timey or any other circumftances, as ex- 
pofure to the air^ light, &c. might make irk 
it, Thefe circumftances, hov/ever, and, as 
I thinki more efpecially the laft, make a 
moil: eflential difference in the cafe, and 
fhould be particularly attended to "when an 
account is taken of the air that any kind of 
%vater naturally yields, I am confident, from 
the experiments I have made at difi^'erent 
times on my own pump water, hinted at 
above, that the air contained in it is in dif- 
ferent, frates at different times. I am alfo fa- 
tisfi^d that the fame is true with refped to 
the water of the Hot- well at Briflol. 

Having my felf examined the air contained 
in the Bath water, as will be i^^vx Vol.1, p. 222> 

I was 

"Dephlogtfttcafed Air, 355 

1 was willing to make the fame experiment 
on the water of Briftol hot-well, and did go 
to Briflol partly with a view to it -, but find- 
ing I had not fafficient time, I defired Mr. 
Becket, on whofe fkill and care I could in- 
tirely depend, to m.ake the experiment for 
me. He was fo obliging as to undertake it, 
and he fent me the fatisfadiory account con- 
tained in his letter to me, which will be 
found in the Appendix to this volume, where 
it will be feen that the air expelled from this 
water was better than common air. 

This being the iirft fadt that I had met 
v/ith of the kind, I requefled that he would 
fend me a quantity of the v/ater taken frefh. 
from the fpring, and then bottled, and care- 
fully fealed up immediately. He did fo, 
and the moment it came to my hands I open^ 
ed one bf the bottles, and flipping into it 
another cork, provided with a glafs tube 
properly bent for the purpofe, and plunging 
the whole in a pan of water, I made it boil % 
and expelling all the air I could from it by 
this means, I found it rather worfe thaa 
common air, but to contain no fixed air. 

Aa 2 I thea 

35^ Ohfervations on 

I then expofed a quantity of it in a phial 
without a cork in a South window, and two 
months after I examined it, together with 
another quantity of the fame water> which 
had been kept corked in the fhade; when I 
found the air in the former fo pure that one 
meafure of it and one of nitrous air occupied 
the fpace of one meafure 3 whereas the air from 
the latter, which had been kept corked, and 
in the ihade, was both lefs in quantity, and 
worfe in quality, being juft what I had iirft 
found it to be, viz. worfe than common air; 
but, as then, without any mixture of fixed 
air. This experiment is another confirma- 
, tion of the influence of expofure to the air, 
if not to the light, on air contained in water. 
Being now fully fatisfied that air is puri- 
fied by being retained in water expofed to the 
air and light, I regretted exceedingly that I 
had not made the obfervation before I was at 
Lymington, that I might have made a trial 
of the air contained in fea water, in the heat 
of the late fummer. I immediately, how- 
ever, wrote to fuch of my friends as either 
had opportunities of making the proper ex- 

Vegefatim. 357 

periments themfelves, or of procuring them 
to be made by others, and particularly to 
my friend. Dr. Percival, whofe zeal to pro- 
mote all fcientifical purfuits is fufficiently 
known, requeiling that he would afk the 
favour of Dr. Dobfon, or fome other friend 
at Liverpool. The Dodrorwas fo obliging 
as to go through the examination with- 
out delay, and with every requiUte pre- 
caution, as will be {qqh by his own letter 
in the Appendix', and he then found the 
air of fea water to be better than common 

I wiih the experiment may be made at 
more places, and at diiferent times of the 
year. I have little doubt, however, but that 
there will be fufficient reafon to conclude, 
that air being imbibed by water^ and efpeci- 
ally by waters of fo immenfc an extent, and 
fuch full expofure, as thofe of the fea, and 
again emitted, comes out depurated, and free 
from the principle with which it was charg- 
ed by animal refpiration, putrefadive pro- 
cefTes, ignition of inflammable fubftances, 
&c, and therefore that the obfervation will 
A a 5 be 

35^ ^ Obfervafwts on 

be of considerable value. Perhaps it will be 
imbibed by water in winter, and emitted in 
fummer, though the ternperature of the fea 
does not vary fo much as that of bodies of 
water of lefs depth and magnitude. 

At the time of my firil: publication on the 
fubjed: of air, I concluded that it was '' not 
*' improbable, but that the agitation of the 
*^ fea, and of large lakes, might be of fome 
** uf^ for the purification of the atmofphere, 
*' and that the putrid matter contained in 
*' water might be imbibed by aquatic plants, 
** or be depofited in fome other manner.'* 
Vol. I. p. 98. This was advanced in confe- 
quence ^ of my having found all kinds of 
noxious air to be depurated to a certain de- 
gree, fo as to be rendered fit for refpiration, 
by agitation in water ; but I had no idea at 
that time of the effedt of water on air being 
fo great as I now find it to be. Indeed, I 
then attributed this efFedl to the mere con^ 
ta5i of the air with the water, and not to 
its being properly abforbed by the water, 
and for a time incorporated ^ith it. 

It will 

Ve get at ion, ' Z19 

It will probably be imagined that tbe j:e- 
fult of the experiments recited in this fec- 
tion, throws fome uncertainty on the refult 
of thofe recited in this volume, from which 
I have concluded that air is meliorated by 
the vegetation of plants, efpecially as the 
water by which they were confined was ex- 
pofed to the open air, and the fun in a gar- 
den. To this I can only fay, that I was not 
then aware of the eiFed: of thefe circum- 
ilances, and that I have reprefented the naked 
faSis, as I obferved them ; and having no 
great attachment to any particular hypothejis, 
I am very willing that my reader fhould 
draw his own conclufions for himfelf. 

I mufl inform him, however, that my ex- 
periments at Leeds were made in a North 
window of the houfe, where the influence of 
the light on the water could not be very 
confiderable, that fome of the procefles were 
completed in two days, and generally in about 
a week 3 and that the v/ater within the jars 
was fo' fmall, in proportion to the quantity 
of air, that I do not at prefent imagine that 
the melioration of air at that time could 
A a 4 have 

360 Obfervations on 

have been owing to it. Befides, as I have 
obferved, I frequently kept air in the fame 
expofure, with refped: to water, light, and 
every other circumftance that occurred to me 
to attend to, and the fame fpace of time, but 
"w^ithout any plant vegetating in it, when 
there was no fenfible melioration of it. 


Of Inflammable Aivi 

I. Of the ProduSiion of Infiammahle Air front 
Iron and a Solution of Galls, 

NFLAMMABLE air was procured by 
Mr. Cavendifh from iron, zinc, and tin, 
hy the vitriolic and marine acids. At the time 
of my former publications I had procured it 
from copper and lead by the marine acid, 
ifom a great variety of animal, vegetable, 
$md mineral fubilances containing phlogif- 
ton, when diiTolved in marine acid air, from 
fome of the metals dilTolved in the vegetable 
acid, and alfo from feveral of them by mere 
^eat with a burning lens, or in a common 


Inflammable Air. ^61 

fire. I now frequently find it an Inconveni- 
ent confequence of heating things in a gun 
barrel. For fome inflammable air, difcharg- 
ed from the iron, mixes with the air that I 
am procuring, in fuch a manner, as to make 
the refult of the procefs a little uncertain j 
fo that, in all experiments that require much 
accuracy, I ufe fmall glafs retorts, or glafs 

Since my laft publication I have procured 
inflammable air, in a confiderable quantity, 
by diflx)lving iron filings in a folution of 
galls 5 and very probably the fame would be 
produced by means of any other aftringent 
fubftance. Indeed mofl things that really 
decompofe the metal, and do not unite with 
the whole mafs of it, will, I imagine, fet loofe 
the phlogifton it contains, in the form of 
inflammable air; though, in feveral of the 
cafes, the phlogifton might join fome of the 
principles in the menftruum, and contribute 
to compofe a diiferent fubftance. 

I was led to this obfervation of the pro- 
du(5tion of inflammable air by the folution 
pf galls, in confequence of being informed 

3 by 

^,62 Objervathns on 

by Mr. Delaval, that ink might be made by- 
putting iron to the folution of galls ; for that 
the acid in the vitriol, which is commonly 
ufed for the^ purpofe of making ink, is an 
unnecelTaiy, and frequently an inconvenient 

Having mixed a quantity of pounded 
galls, iron filings, and water, I firft obferved, 
that, after a day or two, the whole mafs was 
very much fwelled, and that it was full of 
bubbles of air, which it the furface were 
very large. Sufpeding, from the fmell, and 
other circumftances, that the air contained in 
them was inflammable, I burft feveral of 
them near the flame of a candle, and found 
that they all made fmall exploiijns, fo that 
I could have no doubt concerning the qua- 
lity of the air. 

I then mixed three ounces of pounded 
galls with water and iron filings, the quan- 
tity of which I did not note; and covering 
them with a large jar full of v/ater, found 
that, in about a week, they had produced 
fix ounce meafures of air, which was ftrong- 
iy in^ammable, exadly like that which is 


Inflammable Air, ^63 

produced from iron by the acids. In the 
fame manner I procured a quantity of this 
inflammable air by putting the above-meh-^ 
tioned mixture into a. phial with a ground 
ftopper and tube. But this procefs is too flow 
for any ufe. 

Z» Inflammable Air from Oil of Turpentine • 

I have mentioned the property of oil of 
tufpentine to abforb air. Vol. III. p. 112, 
and found that, in its natural fliate, it con- 
tains a confiderable quantity ; but it did not 
occur to me at that time to examine the na- 
ture of the air it contained. Intending to 
profecute the fubjed; a little farther, I lately 
opened a pint phial, half filled with this kind 
of oil, and the cork being very tight, there 
rufhed out of it a great quantity of air, when 
applying the flame of a candle to the mouth 
of the phial, I found the remainder to be 
fl;rongly inflammable. The oil was then 
quite full of air bubbles, and by the heat of 
boiling water I expelled from a quantity of 
it an equal bulk of air, all fl;rongIy inflam- 
mable, like that which is obtained from me- 

364 Ohfewations oil 

tals. It was eight or ten hours in giving 
this air. When I could perceive the colour 
of the flame, I found it to be blue. 

I then took a quantity of the fame kind of 
oil, v^hich had been kept in another phial, 
but I found the air incumbent upon it, vi^ithin 
the phial, to be only common air j but mak- 
ing it boil in a retort, I expelled from it twice 
its bulk of air, all flrongly inflammable. I 
could not difl:inguifh the colour of its flame. 

When I had thus expelled all the air which 
a quantity of this oil of turpentine feemed 
to contain, I agitated it very jftrongly, and 
frequently, in the courfe of two days, in or- 
der to make it imbibe more air, that I might 
expel it again j but I did not find that it had 
imbibed more than a very fmall quantity, 
and this, when it came out again, was only 
common airflightly phlogifticated. The firft 
boiling had made it brown, and very vifcid. 

3. Whether there be any Acid in InJIam^ 
mable Air, 

\n my firft publication on the fubjed of 
air, I had concluded, that it confifled of 


Inflammable Air. 365 

acid and phlogifton, together with fome 
earth. Afterwards, having got the fame air 
without any acid, by heat only, I was fatis- 
fied that the acid was not a neceffary ingre- 
dient in its compoHtion -, and I was farther 
confirmed in this opinion, by finding that, 
when I mixed inflammable and alkaline air 
together, they formed no fort of union. 
For when the alkaline air was abforbed b/ 
water, the inflammable air was left jufl as 

This obfervation has been contradided by 
Dr. Higgins, who pretends to have proved 
the prefence of an acid in inflammable air 
by a great cloudinefs that attends the mixing 
of it with alkaline air. This, I own, would 
be a decifive proof of the alkaline vapour hav- 
ing met with fomething acid in the inflam- 
mable air. But having repeated the experi- 
ment with the greatefl: care, and with cir- 
cumftances which render my obfervation 
more accurate and decifive thanHbefore, I am 
fatisfied that Dr. Higgins, negleding the 
precautions, that are neceffary to be applied 
in thefe experiments, has made fome miflake. 


366 Obfervatlons on 

Iconjedlurethat, making the inflammable air 
with a pretty flrongacid, either the vitriolic, 
or marine, he produced a quantity^of acid air 
together with the inflammable air; and, 
without feparating them by water, admitted 
the alkaline air to that mixture. It would 
then, of courfe, unite with the acid air, and 
form the cloud that he defcribes. But if, 
after this, he had feparated the alkaline 
air by water, he would have found the 
inflammable air unchanged in its bulk or 

The manner rn which I made the experi- 
ment, which I think proves decifively that 
there is not necejfarily any acid in inflam- 
mable air (at leaft, none in a ftate to admit of 
its being decompofed by the mixture of al- 
kaline air) was as follows. Having produ- 
ced the inflammable air in the ufual manner* 
with a weak vitriolic acid, making the air 
to pafs through water, and keeping it in wa- 
ter fome time, that the fuperfluous acid (if 
there fhould have been any in it) might be 
abforbed, I transferred it, by means of a 
bladder, into a jar previoufly filled with 


hiflammable Air, 367 

quickfilver, and {landing inverted in a 
trough of quickfilver. The alkaline air 
was alfo contained in a jar ftanding in the 
fame trough. Then taking a meafure of 
one, and the fame quantity of the other, 
and mixing them in a jar previoufly filleci 
with quickfilver, and, two of my friends 
being along with me, we obferved that 
there was not the leafl: cloudinefs occaiioned 
by the mixture. When they wxre toge* 
ther they occupied exad:ly the fame fpace 
that they had done when they were fepa- 
rate ; and, afterwards, water being admit- 
ted to them, the alkaline air was abforbed, 
and the inflammable air was left undimi- 
nifhed ; and, as far as I could judge, it was 
in all refpedis, the fame that it had been 

4, Inflamfnabk Air not offered by the 
EleSiric Spark, 

Inflammable air is the only kind of air 
that is not affected by the eleSlric /park or 
explofion. This I had obferved before i 
but I have fince made the experiment i^o as 


36S Obfervations on 

to fatisfy myfelf more fully with refpedl to 
it. I confined a very fmall quantity of 
this air in a glafs tube, the diameter of 
which was not much more than one 
tenth of an inch, and the length of the 
column of air did not exceed half an inch, 
and it was confined by water tinged with 
the juice of turnfole. In this fmall quan- 
tity of air I took the eledlric fpark half an 
hour, from the large and powerful machine 
mentioned on a former occafion, without 
producing the leafl fenfible change in Ithe 
dimenfions of the air, or in the colour of 
the liquor in which the fpark was taken. 
I therefore think I may fafely conclude^ 
that inflammable air, at leaft that which is 
produced from iron by oil of vitriol, is of 
fuch a conftitution, as to be incapable of 
being decompofed by this procefs, 

5. Inflammable Air decompofed by Heat, in 
T!ubes of Flint Glafs, 

This kind of air alfo remains unchanged 
when it is expofed to heat in a tall jar of 
flint glafs, in which it had free liberty to 


InJlammaMe Air. ^69 

^?cpa{j4> \ made this experiment at the 
fitiiie tjme with the fjmikr one that has 
heen njentioned before on nitrous air. 
This ajf, as well as the nitrous, recovered 
lX% former dimeniioiKs when it was cold, 
a^id appeared to be ifnchanged in its qua- 

;A y^ry iingukr decompofition of inflam*- 
p^^h^e ^ir I obferved in confequence qf .^x^ 
^qXmg a great variety of fubflances to the 
i,n;fluei)C'e of a fand heat, which I kept up 
ioiir fpveral months. ' Among other things, 
J buriq4 ill this -hot fand glafs tubes |ier^ 
meticfily fealed, and previoi4% filled v^ith 
aU, ,th^ different I^inds of air. I filled 
them i(i the follovy^ing manner. • 
. Having provided myfelf with glafs tubes 
a^ut four feet long, and about one- third 
or one, half of an inch in diameter, and of 
fuch a thicknefs as that I coul^l eafily melt 
tlijer^,\^ith the. flarne of a couple of candles 
^iid ^ , common blow pipe,' I firit fealed 
tfe; tubes at ope end, then filled' them with 
qui^l^firlverj apd placed them inverted in a 
b^^bijk of the i'^i'^r After this^ either trans- 
B b ferring 

37© Obfervatwns on 

ferring the air in a bladder, from the jars 
in which they had been ftanding in water, 
or generating the air a freih, if it was of 
a kind not to bear the contact of water, I 
filled the tubes completely with the kinds 
of air on which I wiflied to make the ex- 
periment, difplacing the quickfilver. This 
being done, I inclined the tube, and apply- 
ing the flame of my candles with fomc 
care (holding the blow pipe in my mouth 
only, and keeping firm hold of the tube 
on each fide of the place to which I was 
applying the heat) I melted the glafs, and 
took off what lengths of it I pleafed -, and 
every piece was, of courfe, hermeticaHy 
fealed. Thefe pieces I marked with a file, 
keeping an account of the meaning of the 
marks, that when I took them out of tha 
fand, I might prefently know with what 
kind of air they hajd been filled. 

When I was performing this part of the 
procefs with inflammable air in flint glafs 
tubes, I obferved that the places to whicji 
I applied the heat were generally tinged 
black; but I gave little atteation to this 


Injlammabk Air, 371 

circumflince, thinking it might be fome- 
thing accidental ; and without any particu- 
lar expedation, I buried thefe tubes in the 
fand, together with the others. This was 
on the 25th of September 1777. 

On the 20th of January following, I 
examined thefe tubes, together with every 
thing elfe that had . been expofed to the 
fame heat. The tube containing the in- 
flammable air was ten inches long, and hy 
fome accident was broke; but it was jet 
black throughout. At this I was very 
much furprized, but I did not then fufped: 
that it was at all owing to the inflammable 
air with wjiich it had been filled ; thinking 
it might have been occafioned by fome 
phlogifliic matter in the fand, or in fome of 
the veflels that had burfl in it§ neighbour- 

Refledling, liowever, on this odd clr- 
cumfl:ance, and thinking, from the uni- 
formity of the tinge, that, pojfibly, it might 
have been occafioned by the inflammable 
air, I filled another fmall glafs tube with 
the feme air ; and, fealing it hermetically, 
^ b 2 buriei 

^72 t>bferva.tions on 

buried it deep in fand, contained in an iron 
pot, which I fet on the fire, and made very- 
hot, nearly red -, and taking it out the next 
day, I found the tube quite black, except 
a fmall part on one fide qf that end which 
had been uppermoft, about two inches 
higher than the othet, and confequently 
had not been expofed to fo great a degree of 

Being now fully fatisfied that the black* 
nefs of the tube was certainly occalioned by 
heating the inflammable iiir within it, in 
circumilances in which it could not expand, 
I proceeded to examine the ftate of the air. 
But, in the firil place, toaffure myfelf there 
had been no cornmunieation between that 
air and the external, air, by means of fome 
unperceived crack in the gl^afs, I plunged 
it in water, and exhaufting the air QV.e£ 
it, did not perceive that any b.ubbJi£>. .ef- 
* caped. , Then breaking the end of the tube 
under w^t^^" I examined it and found it not 
tQ. b^ inflamjuable. Sometimes, however, 
\Yh?n \ have, only made the tube juft blagk 
t^ifpughoMf,,. by applying the flaraeof a 
(; J * ■- V, candle. 

Inflammable Air^ 373 

candle, with a blow pipfe, to every part of 
it, in fucceffion, the air has ftill been in- 

Putting two glafs tubes, about four inches 
in length, and a quarter of an inch in dia- 
meter, itito a fand furnace, I kept them in 
it two days j when I took them out, and 
obferved that the tube which I had placed at 
the bottom of the fand, in the greateft de- 
gree of heat, was nearly melted, arid per- 
fe^ily blue, like indigo -, while the other 
tube, which had not been expofed to fo great 
a degree of heat, was of a beautiful jet 
black throughout. 

Examining the air in thefe tubes, I found 
that in the black tube reduced to one 
third of its bulk, and mere phlogifti- 
cated air. It did not make lime water 
turbid, was not affedled by nitrous air, and 
was not inflammable. The air in the blue 
tube, or that which had been expofed to the^ 
greateft degree of heat, was reduced to the 
quantity of a very fmall bubble, fo that no 
Experiment could be made upon \t. I have no 
doubt, however, that it was plilogifticated. 
B b 3 At 

374 Obfer '■cations on 

At one time I had a fufpicion that this 
blacknefs communicated, to the glafs was 
fomething precipitated from the iron, by 
the folution of which the inflammable air 
had been made; but I was foon convinced 
of the contrary, by finding that the effect 
was the very fame when the inflammable 
air was made from zinc, 

I foon found that there v/as no occafion 
for fo long a procefs to produce this cfl?ed;, 
at leaft upon the glafs. For it began to be 
difcoloured the moment it was red hot, or 
rather when it became foft ; as was evident 
by holding one of the tubes in an open fire, 
or in the flame of a candle. For wherever 
the heat was applied, the blacknefs imme-^ 
diately took place, without afFed:ing any 
ether part of the tube. 

When I examined this black tinge nar- 
rowly, I found that it did not penetrate the 
glafs ', but formed a delicate fuperficial 
tinge, leaving the glafs as perled:ly polifhed 
as before the procefs. But the blacknefs 
was indelible : at leaft it could not be fcraped 
off without tearing the furface of th« glafs, 


Inflammable Atr* 37^ 

and it made no change in it with refped: to 
eled:ricity. For the tube thus blackened 
was as perfe(5t a non-condu(5tor as ever. 

The blue colour of the glafs that was 
moft heated, Mr. Delaval informed me, was 
owing to fomething of iron in the compofi- 
tion of the glafs » That it alfo depended 
upon the degree of heaty J afcertained by 
placing one of theie tubes in a vertical 
polition in the fand heat. For the lower 
end of the tube, which was moil heated, 
had acquired a deep blue colour, and it 
pafTed into the black at the upper end qf 
the tube without any intermediate colour. 
There was alfo no other colour higher than 
the black i fo that ,the firft tinge that the 
glafs receives is a pcrfed black. Yet view- 
ing the firft tinge that it receives by the 
light of a candle placed beyond it, it feem- 
cd to have a fliade of red. 

As I was fenfible that the blacknefs was 
owing to the precipitation oi phlogijion from 
the inflammable air, I thought it poffible 
that fome fubftance which had a near affinity 
with phlogifton might difcharge it i and 
B b 4 ^O'^E 

376 Obfervattons on 

trying minium, it fucceeded immediately. 
Having filled one of thefe black tubes with 
this metalic calx, the moment i made it 
red hot, the blacknefs intirely difappeared, 
and left the tube as tranfparent as ever it 
had been. 

In the £ril experiment of this kind I 
iifed minium out of which all its air had 
been expelled by heat, and which is of a 
yellow colour. In this procefs it became 
whiter, and adhered a little to the glafs. 
When I fcraped it off, I could not be quite 
fure that any part of it was become real 
lead 3 but it evidently approached towards 
a metalic ftate, by being of a more com-* 
pad: texture than before. 

In this fcate of the experiments I com- 
municated the refult of my obfervations to 
-my friend Mr. Bewly, who fuggefted to 
me, that, probably, it was th^ lead in the 
glafs tubes that had attraded the phlo- 
gifton 'y and I prefently found this to be 
the cafe. For when I had filled a ffreen 
glafs- tuhQ with the inflammable air, and 
fealed it herm.etically, as I had done the 


Inflafnmable Air. 2,7'7 

fliftt glafs tubes, I expofed it to a melting 
heat> which is greater thai! that which 
flint glafs "^ill bear, without producing 
any change of colour itl it. What rerriaift- 
cd of the air in the tube, that did not 
efcape when part of it was melted, was 
ftill ftrongly inflammable. 

It appears, therefore, from this experi- 
ment, that the calx of lead, in the form of 
glafs, has a fl:ronger afiinity with phlo* 
gifl:on than any thing in the compofition 
oi inflammable air, in a degree of heat 
capable of melting glafs. Or, if there be 
no proper confl:ituent part of inflammable 
air befides phlogifl;on, the attraction of the 
cal:^ is fo great, as to reduce the phlogifl:on 
from an elafl:ic and uncombined ftate to a 
fixed and combined one. 

Having, by means of thefe glafs tubes, 
effected a complete decomjpofition of inflam- 
mable air, the phlogifton in it having united 
with the glafs of the lead ; I thought that, 
if there had been any acid in its compo- 
fition, it would then be difengaged, and be 
found in the tube. In order fo find whe- 

37^ Obfer'uations on 

ther there was any acid in it, or not, I poured 
into one of thefe tubes a fmall quantity 
of water made blue with the juice of turn- 
fole; but it came out as blue as it went in. 

5. Injiammable Air dinnnified by CharcoaL 

In purfuance of the Abbe Fontana's ex- 
periment on the abforption of air by char- 
coal, I dipped pieces of hot charcoal into 
a phial oT inflammable air, and immediately 
inverted it in quickfilver. When one 
third of the whole quantity was imbibed, 
I found that both the remainder, and that 
which was again expelled from the char- 
coal, by plunging it in water, were inflam- 
mable ; the former not to be difliinguiflied 
from what it had been, but the latter a 
little lefs inflammable. 

6. Whether inflammable or nitrous Air eon^ 
tain more Phlogifion. 

It is well known that both nitrous and inr 
flammable air contain phlogiilon, but in very 
different fiatesjhtzxii^ their fpeciflc g.^aYi'ti,es, 


Inflammable Air. 379 

and other properties^ are mofl remarkably 
different. Many fchemes have occurred 
to me to afcertain the proportion of phlo- 
gift^n that each of them contains -, arvd at 
length I thought of attempting the folution 
of this problem by the help of that ingeni- 
ous experiment of Mr. Warltire's, men- 
tioned in the Appendix to my third volume 
p. 367, viz. burning inflammable air in a 
given quantity of common air. For though 
inflammable air will not part v^ith its phlo- 
giilon to common air when cold, it will, 
like other combufl:ible fubflances, when 
heated to a certain degree. It is then de-^ 
Gompofed, and the phlogiflon that entered 
into its compofition phlogiflicates the aif 
in which it is burned; and the degree of 
phlogiftication may be meafured by the teft 
of nitrous air. I, therefore, proceeded as 

In an eight ounce phial, containing 
many nails, and a quantity of water with 
oil of vitriol, I produced inflammable air ; 
and making it burn with a fmall flame, at 
the orifice of a glafs tube through which 


380 Obfervations m 

thd ait was tranfmitted (being cemented in- 
to the. cork oi fhe phial) I covered the flame 
with a receiver that contained twenty-one 
ounce meafures of air, flanding in water. 
After fix minutes, the flame Went out ; \^hen, 
immediately catching the air that was pro- 
duced in the next fix minutes, and alfo in 
the fix minutes following, I concluded that 
i'^vtrv ounce meafures had been produced, 
ahd ddcompofed, during the fix minutes in 
which it had continued to burn. 

Then examining the air in which it had 
burned, I found it fo far phlogifi:icated, that 
equal meafures of it and of nitrous air ogcu« 
pied the fpace of 1.65 meafures; and com- 
mon dr mixed with one third as much nitrous 
air, being agaift mixed in equal proportions 
with the fsime frefh nitrous air, occupied the 
fpace of 1.68 meafures. It appeared, there- 
fore, that the 21 ounce meafures of air, hav- 
ing received the phlogifticated of one third 
Is much inflammable air, vi^. feven ounce 
meafures, was about as much phlogiflicated as 
it would have been with a mixture of the 
fame proportion of riitroug air. Confequent- 


Injlammable Ait, 

ly, equal meafures of nitrous and inflam- 
mable air cqntain about equal quantities of* 

Of tkis curious problem, however, I have 
obtained a more accurate folution from the 
mode of e:xperimenting introduced 'by that 
excellent f hilofopher Mr. Volta • who fires 
infiammable'air in common air, by theelec^^ 
trie ipark, and confequently can determine 
the'exadt proportion of the inflammable air 
decompofed in a given^ quantity of common 
air. The refult of this p'rocefs agreeing with 
that of the former, leaves little doubt with 
refped: to the conclu-fion I have drawn 
from them. 

Having prepared a ftrong glafs tube,' in 
one end of which I had cemented a piece of 
wire, I filled it with water, knd introduced 
into it another piece of wire, fo as to come 
within about half an inch of the former wire, 
that ari eleiflric explofion might eafily pafs 
between them. 

Into this tube, thus prepared, I transfer- 
red, in the firfl: place, one meafure of in- 
flammable air, and three of common air ; and 


3S2 -Obfervafions on 

then, by. means of an eled:ric exploiion be- 
tween the wires, in the central place of the 
air, I iired all the inflammable air, which 
would then be decompofed, and, of courfe, 
part with its phlogillon to the common air 
with which it was mixed. After the explo- 
ffon, laccordingly found it to be complete- 
ly phlogiflicated. This alfo would have 
been the confequence of. mixing the fame 
proportion of nitrous air with the common 
air. But to determine the problem with 
accuracy j it was neceiTary to ufe fuch a pro- 
portion of inflammable as would only phlo- 
gifliicate the common air in part. 

I therefore mixed one meafure of inflam- 
mable air with three meafures of common 
air, and after the exploflon found it be fo far , 
phlogiflicated, that one meafure of this and 
one of nitrous air occupied the fpace of 1.8 
meafures -, and this I alfo found, by the fame 
teft, to be exadily the ftate to which a mix- 
ture of one meafure of the fame nitrous air 
brought three meafures of the fame common 


tnflammahk Air. 383 

In order to obtain a farther confirmation 
of my conclulion, I mixed one meafure of 
inflammable air withyoar meafures of com- 
mon air 5 and after the exploiion I alfo 
found, by the tefl of nitrous air, that it was 
phlogiflicated exactly as much as by the mix- 
ture of an equal quantity of nitrous air. And 
repeating the experiment with the fame pro- 
portion of inflammable and common air, I 
found that after the exploflon the air wa^ 
diminifhed, without mixing with nitrous air, 
juft as much as one meafure of nitrous air di- 
minifliedfour meafures of commgn air, ijiz, 
from 7.4 to 5.2 meafures. 


^§4 QbfenmttQm &n 

S E C *r I p N XXXV. 
Qf Fixed Air. 

I. Of the Generation of Fixed J^ir from 
the Vitriolic Acid, 

AT the time of my lafl publication \ 
think I, h^d clearly afcertained th^ 
generation of fixed air from fpirit of nitre, 
^^d various other f^bftances, which hay^ 
never beeji fufpedted to contain it, fuch ^^ 
fpirit of wjne, &c. J have now as evidej^l 
a proof of the generation of fixed air frqEqi 
the vitriolic acid united with fpirit of wine, 
or with ether, which is produced from 
them both ; fo that thefe two acids, viz, 
the vitriolic and nitrous, agree in being capa- 
ble of forming both dephlogiflicated and 
fixed air ; a circumftance which may throw 
confiderable light on the conftitution of 
thefe acids, and the relation they bear to 
each other. 

After going through the procefs for 
making ether, from concentrated oil of 


Fixed Air. 385 

vitriol and reclified fpirit of wine, I had 
the curiolity to pufh the procefs as far as it 
would go, in order to examine whether 
any kind of air would be yielded in any 
ftage of it. I therefore continued the dif- 
tillation till the whole reliduum was con- 
verted into a black mafs, full of grofs 
niatter 5 and taking as much of the black 
lumps as filled about one-fifth of an ounce 
meafure, I put them into a tall glafs vefTel, 
and diftilled them to drynefs in a red hot 
fand heat. 

The firft air that came over was the 
common air a little phlogifticated, then 
the vapour of the watery part, and after 
that a large quantity of air at firfl clear, 
but towards the middle of the procefs very 
turbid and white, but clear again at the 
laft. I received in all about a pint and a 
half, in four portions, each of which con- 
tained about four-fifths of fixed air, and 
the reft inflammable, burning with a blue 
flame ; but the proportion of fixed air was 
fomething greater in the middle portions 
than either in the firfl or the laft. I 
C c thought 

386 Ohfer'uations on 

thought it poffible that the cork, with 
which, as well as with clay and fand, the 
glais tube was joined to the glafs veffel 
that contained the materials, might fupply 
the inflammable air in part, as I perceived 
it was corroded and become black. It may 
be worth while to repeat this procefs in a 
glafs retort. 

Having gone over this procefs with fpirit 
of wine, I recolledied the black matter 
that was produced when I got vitriolic acid 
air from vitriolic acid and ether -, and there- 
fore determined to repeat that procefs and 
carry it farther; to fee whether I fhould, 
in any part of it, get fixed air, as in the 
preceeding experiment with the fpirit' of 

I therefore put one-eight part of vitriolic 
ether to a quantity of freih diflilled oil of 
vitriol, and in a glafs phial with a ground 
ftopper and tube, and with the heat of a 
candle, I got from it a great quantity of ' 
air, part of which was vitriolic acid air, 
v/hich was abforbed by the water^ but I 
©bferved, as the procefs advanced,, the part 


Fixed Air, 387 

that was not readily ab for bed by water kept 
increafing, till at length the greater part of 
the produce was of this kind ; and in the 
middle of the procefs it was very turbid*, 
Examining this air it appeared to be fixed 
air, making lime water turbid, and being 
readily abforbed by water -, but there was 
a refiduum of phlogifticated air, about one- 
lixth of the whole. 

I then put the remaining materials, which 
were about an ounce meafure, into a glafs 
veiTel ; and with a fand heat I colledted 
much more air than before, about two pints 
in all, the firft part - of which was the 
purefl: fixed air I had ever feen, having the 
fmalleft refiduum. The lafl portion had 
more refiduum, and this burned with a 
lambent blue flame. But this inflammable 
matter might pofiibly come from the cork 
with which the veflTel was clofed, as be- 
fore ; though I think it not fo probable. 
At lafl: the procefs was interrupted by an 
accident ; but I concluded, from feveral 
circumfl:ance's, efpecially from the time 
that elapfed before the vapour ceafed to 
C c 2 ifiue 

388 Obfervafions on 

ilTue from the orifice of the velTel (which 
continued buried in the hot fand) that more 
than twice the quantity of air might have 
been colledled. The air had been very 
cloudy before the laft portion, which con- 
tained the refiduum of inflammable air. 

From this experiment, efpecially that 
with the ether, in the glafs phial and 
ground ftopper, I think it is pretty evident, 
that fixed air is a faSiitious fubjiance, and 
that the vitriolic, as well as the nitrous 
jicid, may be converted into it. 

2. Of Fixed Air imbibed from the At" 

From a folution of quickfilver in the 
nitrous acid, which had flood expofed to 
the air a confiderable time, I once got a 
confiderable quantity of fixed air, together 
with that which was cjephlogifticated (See 
Vol. III. p. 352) whereas I never got any 
fixed air when I made the diftillation im- 
mediately after the folution. It was moll 
probable, therefore, that the fixed air had 


Fixed Air, ' ^8,^ 

been attracted from the atmoipheFe. How- 
ever, as it was pqffible that this production 
of fixed air might have come from the 
mixture itfelf, in a courfe of time ; efpeci- 
ally as I had found that, in fome cafes, 
fixed air was produced either from, or by 
means of, the nitrous acid, in the decom- 
polition of fubilances that did not contain 
it ; I made a folution of mercury in ftrong 
nitrous acid, and kept it in a phial with a 
ground ftopper from May 1776 to the 12th 
of September following. Pouring this 
folution as quickly as poffible into a fmall 
long necked retort, I got from it, in a fand 
keat, a large quantity of air, firft nitrous, 
and then dephlogifcicated, but no part of 
it was fixed air, not making lime water in 
the fmallcil degree turbid. It was in this 
procefs that I got that exceedingly pure 
dephlogifticated and nitrous air mentioned 
before ; but I do not fuppofe that the 
peculiar purity of it was at all owing to the 
length of time that the folution was kept 
before the diilillation. 

C c q In 

390 Obfervations on 

In Vol. III. p* 3i3> I have recited in- 
ftances of wood afhes imbibing fixed air 
from the atmofphere. To be more fully 
fatisfied with refpedt to it, and alfo the 
quantity of fixed air imbibed by them in a 
given time, I kept the fame afhes, and 
extraded air from them at certain intervals. 
I alfo did the fame thing with feveral other 
fubflances of a fimilar nature, and the refults 
were as follows. 

On the 1 8th of April 1778, I extra(fted 
all the air I could from half an ounce of 
wood afhes, and got about eighty ounce 
meafures, half fixed air,, and half inflam- 
mable throughout ; and on the 25th of the 
fame month I repeated the procefs on the 
fame afhes, in a gun- barrel, and got from 
them twenty ounce meafures of air, the 
greatefl; part of which was fixed ^ air, and 
the refl inflammable. The afhes \vere be-^ 
come almpft: black after the experiment. 
At firfl I imagined it might be the charcoal 
revivified by the phlogiflon from the gun- 
barrel ', but I afterv/ards found it to be a 
kind of glafs, or flag, the heat having 


Fixed Air. ^^r 

been fo great, as to vitrify the ailies i and 
the phlogifton from the iron had given them 
the black colour. 

June the 2d, I extradied, by heat, in a 
gun-barrel, from wood afhes from v^hich 
4iir had often been extracted before, in the 
fame manner, and the laft time on the 9th 
of May preceding, all th€ air that they 
would yield. It was twenty-one ounce 
meafures ^ the firfl: portions of which were 
half fixed air, and afterwards one-third ^ 
the remainder in both cafes being inflam- 
mable, probably from the iron. A good 
deal of moifture diftilled from thefe afhes, 
though they feemed to be perfed;ly dry. 
After the procefs, they weighed 18 dwts. 
and, judging from their colour, not much 
' more than two-thirds of them had been 
affected by the heat. 

On the 23d of Ocftober following, the 
fame wood aflies weighed 19 dwts. 12 grs. 
and I got from them, in a gun-barrel, 
about thirty ounce meafures of air, of which 
more than 25 ounce meafures was pure fixed 
air, the remainder inflammable, burning 
with a blue flame. They had not all been 
C c 4 equally 

392 Obfervations on 

equally affeded by the heat. After the pro- 
cefs, they weighed 1 8 dwt. 6 gr. That they 
had attra6led fixed air is evident, efpecially 
from the laft procefs, in which the greateft 
part of it v/as very pure. 

On the 1 8th of April 1778, I got, from 
an ounce of pit-coal afhes, in a gun barrel, 
nineteen ounce meafures of air, of which at 
firft two thirds, and at the lafl one third was 
fixed air, and the reft inflammable. On 
the 24th of the fame month, I extracted from 
the fame pit-coal afhes (which, as well as 
the wood afhes in the preceding experiment, 
had been expofed to the open air in a difh, 
fo as to lay about half an inch thick) no 
ounce meafures of air; but with mere heat 
than before. Of the firft part of this air one 
third was fixed air, but of the laft hardly 
any, the remainder being inflammable, burn- 
ing with a blue flame -, but fo faintly, that 
probably the greateft part of it was phlogif- 
ticated air. 

Heating the fame afhes over again, in a 
fliallow iron veiiel, and letting them cool, I 
got from them, by the fame procefs, fifteen 


Fixed Air. 3qj 

t)unce meafures of air, one third of which 
was fixed air, and the reft inflammable. But 
I obferved, that when the aihes came out of 
the gun barrel, they had the appearance of 
charcoal, but upon farther examination, I 
found it to be glafs or flag ; thefe allies hav- 
ing been vitrified by the heat, and having 
received phlogifton from the iron, as in the 
preceding procefs with wood afhes. But 
thefe aflies from pit-coal are vitrified with 
much lefs heat than the wood aihes. 

Common pit-coal, I have obferved, yields 
no fixed air, though the ajhes do -, but I have 
found that one fpecies of pit-coal, called Bo- 
'vey coal, yields fixed air in the firft inftance, 
which feems to indicate that there is fome- 
thing of a vegetable nature in that coal. 
From half an ounce of this coal I got, in a 
gun barrel, about an hundred ounce mea- 
fures of air, three fourths of which was fix- 
ed air throughout, and the remainder in- 
flammable 3 the firft part of it burning with 
a bright white flame, like inflammable air 
from common pit-coal, the laft part ex- 
ploding like inflammable air from metals, 


- ^ 94 Ohfervations on 

only more faintly. Part of this air had pro- 
bably come from the gun barrel. 

I alfo found that manganefe, which had 
been calcined on the loth of Nov. 1777, 
and again on the 15th of April 1778, yielded 
a fmall quantity of fixed air on the 2d of 
June following. From i oz. 18 dwt. of 
manganefe, which had been kept in a red 
heat a long time I expelled twenty ounce 
meafures of air, all fixed air. This Was in 
a gun barrel, with as much heat as I could 
give to it, perhaps more than I had applied 

The preceding experiments, relating to the 
imbibing of fixed air from the atmofphere, 
were made with vegetable and mineral fub- 
ftances. I made fome obfervations of the 
fame kind on animal fubftances. On the 
24th of Feb. 1777, ^ ^odk i L oz. of bone 
afhes ', and, in a gun barrel, I got from them 
a confiderable quantity of air, half fixed, and 
half inflammable. I then put ipirit of nitre 
to them, and obferved that the mixture was 
attended with great heat, and the emiflion 
of red vapours, and when dry they weighed 

4 2 oz. 

Fixed Air. 39 r 

2 oz. 4dwts. From half of this quantity I 
expelled about a pint and a half of air, 
one-fourth fixed, and the reft dephlogifti- 
cated. There remained little lefs than the 
original quantity of afhes. 

From the iame bone afhes, which had' 
been moiftened with fpirit of nitre, I 
expelled, on the 15th of April 1778, 
about ten ounce meafures of air, about one 
third of which was fixed air, and the re- 
mainder phlogiiliicated. Thefe aihes had 
been kept partly in an open diih, and partly 
in a phial clofe flopped, owing to my re- 
moving from one place to another, and not 
having an opportunity of making the expe-^ 
riments that I intended. On the 2d of June 
following, I extra6led from the fame bone 
aihes five ounce meafures of pure fixed air, 
the fmall refiduum being phlogiflicated. 
They then v^eighed i oz. 8 dwt. 6 gr. 

From an ounce of the bone afhes, from 
which air had been expelled on the 24th of 
Feb. 1777, but not thofe on which thepre-^ 
ceding experiment was made, I got by heat, 
in a gun barrel, on the 15th of April 1778, 


39^ Obfern)ations on 

about fifteen ounce meafures of air, almofl 
pure fixed air. Thefe aflies had been kept 
part of the time in a phial, and partly in an 
open difh, as thofe mentioned above. 

From the fame bone afhes I was not able, 
on the 2d of June, to extract any air at all, 
no*: again on the 23d of 0(5t. following. 

It Ts evident from thefe experiments, that 
thefe bone alhes (and the fame is probably 
the cafe with the afhes of other animal fub^ 
fiances) have not the fame property of draw- 
ing fixed air from the atmofphere that the 
afhes of vegetable and mineral fubflances 
have 5 but that the addition of fpirit of nitre 
gives them that property. This obfervation 
may poflibly be of fome ufe in our inquiry 
into the nature of animalization. 

3. jit tempts to extraB fixed Air from 'va- 
rious Subfiances. 

To the fubflances from which I had en- 
deavoured, at different times, to extradt air 
by heat, it may be juft worth while to men- 
tion crude antimony. From one ounce of it, 
in a glafs veflel, and with a red fand heat, I 


Fixed Air. y^j 

got very little air, not more than its bulk. 
The laft portion was in a great rneafure fixed 
air, and the refiduum extinguiflied a candle. 
The antimony on which this experiment 
was made, and which had been pounded, 
formed a concrete mafs when taken from 
the fire. 

I have before obferved, that with much 
heat I got a little fixed air from pipe clay. I 
thought it was poffible, that when it was 
mixed with the vitriolic or marine acid, it 
might yield more. I therefore tried both, 
but got no^ more air than about the fame 
quantity as before. 

From a quantity o^fuor, in a gun barrel, 
I got a fmall quantity of fixed air, the re- 
fi;duum being phlogiilicated, and at the lail 
inflammable, from the gun barrel. 

I expedled to have got fome air from borax ^ 
and for this purpofe gave it as much heat as 
a green glafs retort could bear; but Igot little 
or nothing more than the common air in the 
retort, though I continued the procefs till 
the glafs melted. 

4. Fixed, 

^98 Obfervatlons on 

4. Fixed Air expofed to Heat, 

I expofed fixed air, as well as all the other 
kinds of air, to a continued heat, and in 
this cafe I made ufe of a green glafs tube. 
I kept it in hot fand a whole day, fo hot that 
one end of the tube was much dilated, but 
-had not burft. Opening it under v/ater, one 
half of the tube was inftantly filled, and the 
remainder was the pureft fixed air. I did not 
pe^xeive any thing depofited on the glafs, as 
in the cafe of the marine and vitriolic acid 

5. Air from Charcoal and Br ecipitate per fe. 

Many perfons, I find, have confounded 
phlogifticated with fixed air, having con- 
cluded the whole of a quantity of air to be 
of the latter kind, though by far the greatefl 
part of it was of the former. This I found 
to be the cafe with refpecfl to the air ifilii ng 
from the ground in the Bath fpring. Vol. II. 
p. 224. I alfo obferve a miflake of the fame 
kind made by Mr. Lavoifier; which my 
friends think it may be of fome confequence 


Fixed Air, -59^ 

to correal j he having inferred from it, that 
** common air is changed into fixed by the 
*' addition of phlogiftonj* See Rezier's 
Journal, Vol. V. p. 432. 

He mixed an ounce of precipitate per fe 
with 48 grains of charcoal, and then got 
from it air which had the five follow^ing 
properties, i. It combined with water, and 
made it acidulous. 2. It was fatal to animals. 
3. It extinguifhed a candle. 4. It precipi- 
tated lime in lime water. 5. It united with 
alkalis, fixed and volatile, deftroying their 
caufticity. *' Thefe properties," he adds, 
** are precifely thofe of that fpecies of air 
*' which is known by the name of fixed, or 
** mephitic air, fuch as is obtained from all 
•* metalic calces, with the addition of char- 
'* coal, and fuch as is difengaged in fer- 
** mentation." 

That fuch a mixture of precipitate and 
charcoal would yield air which had the pro- 
perties abovementioned, I had no doubt ; 
but I was likewife well fatjsfied, from my 
experience in thefe matters, that the ivhok 


400 Ohfervations on 

produce would not be fixed air, Kut contain 
a great proportion of other kinds of air, in 
fad, the very fame that thefe materials would 
have yielded feparately -, the dephlogifticated 
air from the precipitate being depraved by 
the mixture of the other kinds of air. 

However, for the fatisfad;ion of my 
friends, who thought the experiment of 
confequence, I mixed i dwt. of precipitate 
per fe with half a pennyweight of well 
burned charcoal i and putting it into a green 
glafs retort, expelled air from it, (but not 
all that it would have yielded) receiving the 
produce in different portions> when I found 
the firft was three fourths fixed air, with 
the refiduum inflammable. The fecond was 
about as good as common air ; and the third 
was phlogifticated. AH this, however, 
mixed together, would have exhibited the 
appearances (or veiy nearly fuch) as Mr. 
Lavoifier has defcribed. 

As to the conclufion of Mr. Lavoifier's 

paper, in which he improperly ftates it aa 

' my opinion, that fixed air is a compofition 


Cream of Tartar, 401 

of common air and phlogifton. I have ani- 
madverted upon it in my fecond volume, 

P- 313- 

SECTION xxxvr. 

Experiments on Cream of Tartar. 

"^ A R T A R is a fubflance concerning 
which there has been a great dever- 
lity of opinions among chemifts. ^ On this 
account fome of my chemical friends re- 
queued that I would examine what kind of 
air it yielded in different circumftances. 
Accordingly, to fatisfy them, and my owa 
cufiofity at the fame time, and without any 
particular expeftation, for I had formed no 
opinion whatever with refpe(fl to it, I began 
with putting a fmall quantity of the cream 
of tartar into fome oil of vitriol, contained 
in a phial with a ground ftopper and tube, 
(which is the method that I ufually employ 
to procure vitriolic acid air) and, with the 
ilame of a candle, I made it boil. 

. D d ^ Ths 

402 Ohfervafions on 

The acid prefently became black, and the 
mixture yielded a great quantity of air, till 
it was quite vifcid; when, there being fome 
danger of choaking the tube, I withdrew it. 
The air was at firft half fixed air, making 
lime water turbid, and half inflammable, 
burning with a lambent blue flame 5 but to- 
wards the laft two thirds of it was inflam- 
mable. I did not ufe more than a few penny- 
weights of the tartar, and the quantity of air 
exceeded two quarts, and much more might 
certainly have been procured. The next day 
the matter, which I had poured out of the 
phial, had the confiflency, colour, and fmell 
of treacle; except that there were fome 
fmall concretions in it. Some time after I 
took the refiduum above-mentioned, and 
putting it into a glafs veflel, I again extrad:- 
ed from it, in a fand heat, a large quantity 
of air, as much as before, and exadlly of the 
fame kind. In the middle of the procefs, 
when the produdlion of air was moil co- 
pious, it was very turbid ', and when any of 
the bubbles burfl in the open air, they Were 
perceived to have a flrong fmell of treacle. 


Cream of T! art at. 403 

After this I ceafed to piake ufe of oil of 
vitriol, in order to try what air the tartar 
would yield of itfelf 5 and I prefently found 
that the acid had contributed nothing at all 
to the air that I had got from it. From an 
ounce of cream of tartar, in a glafs vefTel, 
and a fand heat, I got 170 ounce meafures 
of air, the firfl: portions of which were almofl 
pure fixed air. The refiduum, however, was 
inflammable, and burned with a blue flame. 
At lafl: only about two thirds of the air was 
fixed air, and the refl: inflammable. In the 
greatefl: part of the procefs, the air was very 
turbid -y but it was fo in the recipient, and 
the part of the tube next to it, a confider- 
able time before it was turbid in the refl of 
the tube, or in the glafs veflel that contained 
the materials. Towards the end of the pro- 
cefs the empyreumatic oil came over, which 
was very ofFenfive, though, at firfl:, the fmell 
of the air had been rather pleafant, refembling 
that of burnt fugar. 

I repeated this experiment, and again got 

about 170 ounce meafures of air from an 

ounce of cream of tartar, of which 38 ounce 

D d 2 meafures 

404 Obfervations on 

meafures were inflammable, and the refl 
fixed. It burned with a large white flame, 
but at laft with a light blue one, owing, I 
fuppofe, to the mixture of fixed air in it. 

That cream of tartar fhould y loldi Jixed 
■ air will not be thought extraordinary 3 but 
its yielding inflammable air, feems to Ihew 
that it had acquired a good deal of the con- 
fiflience of vegetable matter, orof pit-coal ; 
fince thofe fubftances yield the fame kind 
of ^ air. 

After this, neglecting the produce of air, 
I Amply calcined a quantity of cream of 
tartar, in a red heat, in a glafs veffel filled 
up with fand ; and obferved that it loft 
about half its weight. Notwithftanding its 
calcination in a red heat, this fubftance 
obftinately retained a great deal of its fixed 
air, in which it refembles chalk. For 
when I put this calcined cream of tartar 
into fpirit of fait it yielded a confiderable 
quantity of air, which I found to be fixed 
air, with a phlogifticated refiduum. It 
alfo, effervefced in the fame manner, and 
no doubt gave the fame kind of air in oil 


Cream of T^artar. , 405 

of vitriol, and fpirit of nitre. But even 
fpirit of fait did not diffolve the whole 
of it. 

To obferve the phenomena of this cal- 
cination more particularly, I made the pro- 
cefs in an open crucible, v\^hich I kept in a 
red heat a long time. But when there was' 
no appearance of any farther change, and 
the fubftance was pretty hard, I took it 
from the fire, on which it prefently afTumed 
a blackiih, or dirty brown colour. Spirit 
of fait diffolved this fubftance with as much 
rapidity, to all appearance, as it had done 
the mere black coal of tartar in the former 
experiment, and expelled as much air from 
it. It ftill, however, did not dilTolve the 
whole : for a dirty powder remained undif- 

Whether any chemifl will think thefe 
obfervations of any value I cannot tell. 
Probably they are not of much confequence, 
but I thought it might be worth while jufi; 
to mention them. 

D d ^ SEC- 

40 6 Obfervatlons on 


Mifcellaneous Obfervatlons on Subjia?ices ex- 
pofed to a long continued Heat, 

'Y experiments on expofing fubflances 
to a long continued heat were begun, 
principally, with a view to afcertain the 
converlion of water into earth, of which 
we have many credible accounts, and of 
which that excellent chemiifl Mr. Woulfe 
entertains no doubt. 

For this purpofe I provided glafs tubes, 
about an inch in diameter, and three feet long, 
and alfo others made like what the workmen 
C2}\ proofs, growing narrower to the top, fome 
two inches wide at the bottom, and others 
lefs than an inch. Indeed, I ufed glafs 
tubes of a great variety of forms and fizes, 
and when I had put in the water, or other 
fluid, I clofed them hermetically, and placed 
them in a fand furnace pretty equally heat- 
ed. But,_ in general, before I placed them 
there, I ^xpofed the end containing the 


The Effe5}s of continued Heat. 407 
fluid near a common fire, for a few hours ; 
both to obferve whether there would be 
any immediate change, and alfo to try what 
degree of heat the tube, thus charged, 
would bear. 

The refult of many of the experiments 
made in this manner have been recited, and 
were fufficiently remarkable, and others, 
that do not deferve to be palTed over will be 
noted in the courfe of this fed:ion. But 
with refpedt to wafer, which was my firft 
and principal objed:, all my experiments 
intirely failed ; and yet I do not therefore 
infer that the experiments of others have 
not been faithfully related, particularly 
thofe of Mr. Godfrey. 

In order to avoid expence, I ufed a greater 
degree of heat than had been ufed before 
for this purpofe; hoping, by this means, 
to gain my end in lefs time. Whereas I 
believe Mr. Woulfe's opinion is quite right, 
'viz. that the heat fhould be very moderate, 
and long continued. Mine was confidera- 
bly above a boiling heat in the open air, 
generally fuch as to keep the water boiling 

D d 4 ia 

40 8 ^ Obfervations on 

in this confined ftate, my veffels being 
ilrong in proportion. I went upon the idea, 
that the change of coniiftence in water 
was brought about by extending the bounds 
of the repuhlon of its particles, and at the 
fame time preventing their a(5tually receding 
from each other, till the fpheres of attrac- 
tion within thofe of repullion fhould reach 
them. The hypothelis may ftill be not 
much amifs, though I did not properly a6t 
upon it. 

Be this as it will, a trial of iix months 
had no effed: of the kind that J hoped for. 
It fliould, however, be coniidered, that it 
was ten months before Mr. Godfrey per- 
ceived any change in the conliftence of his 
water, and'fifteen months before its con- 
verfion into earth was completed. 

The particular appearances that I ob- 
ferved would be too tedious to relate, and 
were not of much importance. I fhall, 
therefore, only obferve in general, that I 
was deceived at the beginning of the procefs, 
by finding that the whole mafs of water, • 
which was generally an ounce, would 


The BffeBs of continued Heat. 409 
become exadly lik.« milk, and fometimes 
the whole tube would have got a complete 
white coating in the courfe of a day or two. 
This I then hoped was, in part, a change 
in the water itfelf, though I had no doubt 
but that, in part, it might be owing to the 
corrolion of the glafs by the heated vapour. 
'In the end it appeared to have been nothing 
at all elfe. 

When the heat was a little more mo- 
derate, the iirfl: appearance was a white 
pellicle on the furface of the water, and 
fome times in the middle of the water only, 
not extending to the fides j which deceived 
me the more into an opinion that this ear- 
thy pellicle might come from the water 
itfelf. In time there was fuch an accumu- 
lation of this matter, that it clouded the 
whole mafs of the water, and funk to the 
bottom^ in the form of white flakes, or a 
powdery fubftance. When the tubes were 
opened, all the fides were found corroded, 
the polifh being entirely taken off where 
the heat had been greateft, efpecially near 
the furface of the water. 

I was 

4.10 Obfervations on 

I Was farther deceived by finding, on open- 
ing feme of the tubes occafionally, that when 
I had drained all the moifture I could out 
of them, it weighed conliderably lefs than 
it had done when it was put in, notwith- 
ftanding a good deal of white flaky matter 
was necelTarily poured out, and weighed 
along with the water, as well as a good deal 
left behind; and, with a view to thefe 
occafional trials^, I had moiftened fome of 
the tubes, letting them ftand a fhort time 
to drain before I put in the deftined quantity 
of water. But when the procefs was over, 
\t appeared that much more moifture had 
been entangled in that flaky matter that 
was left in the tube, and which could not 
be drained from it, than I had made allow- 
ance for, and much more than the weight 
of white matter that came out of the tube 
along with the water. 

The force of the vapour of water in thus 
corroding glafs is, however, not a little 
remarkable. In time it would have worked 
its way through any thicknefs of it. And, 
indeed, I fhould obferve, that the fame is 


T^he EffeSis of continued Heat. 411 
the cafe with iron. For before I began 
thefe experiments, I had made a /ew ran- 
dom trials of what might be done with 
water in a JJjort time by a very great degree 
of heat, in a confined ilate, by putting the 
water into gun-barrels, then getting them 
clofed by welding, and after that putting 
one end of them into a hot fire. Some- 
times the water would continue thus a 
whole day or more -, but at length though 
the gun-barrels were the thickeft that I 
could meet with, and one of them was the 
breech of a mufket- barrel, and I believe 
perfe(5tly found, it wore its way through. 
None of the barrels were properly burji, 
but all of them were much corroded, and 
made exceedingly thin in particular places ; 
and when they were opened a great quantity 
of ruft was found in the infides of them *. 
Befides trying the eifedl of this procefs 
on pure diftilled water, I made trial of 


* I fince recoUedl that I formerly had a copper aeoli- 
, pyle, not lefs than the thicknefs of a half crown, which, 
after being ufed a good deal, burft, and was found to 
fce as thiri as paper. 

4 lit Obfervations on 

water impregnated with all the different 
kinds of air with which I am asquainted i 
and in other tubes the air confined along 
with the water was of all the different 
kinds ; but the appearances in the mall were 
nearly the fame, excepting fuch as have 
been, or will be particularly defcribed. 
The common ^ir, in all thefe tubes, in 
which the water had been kept fo hot, did 
not appear to have been changed either for 
the better or the worfe.' Sometimes when 
I foftened a part of a tube with a blow 
pipe, the inclofed air would prefs the glafs 
a little outwards, and fomefcimes the exter- 
nal air v/ould prefs it a little inwards, but 
it was with no great force ; and whenever 
I opened the tubes under water, and ex- 
amined the air, it did not appear to have 
been altered in its quality, with refpedl to 
its diminution by nitrous air. ' 

It is' known, that, in general, a men- 
ftruum will hold more of 2ifohend when it 
is hot, than when it is cold -, but thefe ex- 
periments in a continued heat afford feveral 
remarkable examples of the contrary. The 


ne EffeBs of continued Heat, 413 
firft thing I obferved of this kind was with 
refped: to lime water : for having confined 
a quantity of it in one of my largeft tubes, 
I found that, in fix days, and how much 
lefs time might have fufficed I cannot tell, 
all the lime was depofited. At leaft there 
feemed to he enough at the bottom of ^ the 
water from which it was feparated, to have 
faturated the whole of it. 

Alfo iro7i diliblved in water impregnated 
with fixed air was feemingly all precipi- 
tated, in confequence of being expofed in 
the fame manner to the heat ; and when it 
nvas cold, it was not re-difiblved. For 
though this menftruum will difiblve iron, 
it will not difiblve the calx Qi iron. Per- 
haps the heated' water might take the phlo- 
gifton of the iron into a flate of more 
intimate union with itfelf, as in the experi- 
ments with quickfilver ; in confequence of 
which the calx of the iron, being deferted 
by its phlogifton, mufi: of courfe be pre- 

I had been informed by Mr. Bewly, that 
lime v/ater would difcharge the colour of 


414 Ohfervations on 

Pruffian blue. A quantity of lime water, 
thus impregnated with the colouring mat- 
ter in Pruffian blue, I put into one of my 
glafs tubes on the 1 1 th of Augufl, and oil 
the 23d, from being quite colourlefs, it 
was become of a greeniih colour, with 
many opake particles in it. On the 9th of 
September following it was quite tranfpa- 
rent, with a large white fediment, in which 
it refembled the tubes that had only water 
in them. This fediment, therefore, might 
perhaps come from the, corrofion of the 
glafs. On the 30th of September, the 
liquor was quite cloudy, had a confiderable 

precipitate, and a thick whitifh incruftation 
covered all the furfaceof it. Laflly, on the 
19th of January 1778, it had fomethingof 
a milky appearance, but was nearly tranfpa- 
rent, and had depolited a quantity of flaky 

Having the folution of mercury, and alfo 
of copper in, fpirit of nitre at hand, proper 
tubes to fpare, and room enough for them 
in my hot fand, I placed about an ounce 
meafure of each of them in the furnace on 
A. \ the 

"The Effects of continued Heat. 41^5 
the 9th of September, and on the 30th of 
the fame month I found the folution of 
mercury quite colourlefs as at firftj but I 
fuppofe the greateft part of the mercury was 
precipitated in one beautiful compad: yellow 
mafs. The precipitate of the copper was 
alfo colledled into one mafs, quite blue, 
as the liquor itfelf continued to be \ fo that 
the whole of the copper had not been pre- 

When I took thefe tubes from the fand 
heat for a few days, the greateft part of the 
precipitated mafs was re-dilTolved ; but 
when they were replaced in the fand heat 
they appeared again as at firft j and fo they 
were found on the 19th oi January 1778, 
when an end was put to the procefs. 

On the fubjed of the nitrous acid I fhall 
obferve, that water faturated with nitre, 
which had been placed in the fand furnace 
on the 3d of September, in a long and ilen- 
der glafs tube was tranfparent on the 30th 
of the fame month ; but the tube itfelf, 
fromthe furface of the liquor to half an 
inch below it, and likewife in different 


41 6 Obfervations on 

places quite to the top of the tube, was 
covered with a white incruftation, a little 
inclined to blue. 

Cauftic alkali impregnated with nitrous 
vapour had cracked the tube in which it 
had been confined, and efcaped ; but the 
tube was found covered with a white in- 
cruftation, from two inches above theXur- 
face of the liquor quite to the bottom of 
the tube. The crack itfelf was very re- 
markable, confifting, in reality, of many 
different cracks, and thofe difpofed very 
irregularly, quite round the glafs, near the 
furface of the liquor, I have fometimes 
feen glafs cracked in the fame manner by 
electrical explofions. 

The moft remarkable thing that I have 
obferved, with refped to metallic folutions, 
relates to a folution of gold in aqua regia, 
made by the impregnation of the marine 
acid with nitrous vapour, which I have 
obferved to be a more powerful menftruum 
for gold than the common aqua regia. A 
fmall quantity of this folution I had put 
into a very thick glafs tube about nine 



^he EffeBs of continued Heat. 417 
inches long, and I placed it in the fand fur- 
nace on the 1 1 th of Augufl, and on the 
23d of the fame month I found much of 
the gold precipitated, and adhering to the 
lides of the glafs in the form of (lender 
cryftals, very beautiful. On the 30th of 
September, I obferved no difference in the 
cryftals, but found fome gold precipitated 
in irregular maifes, of a darkifli colour, 
^uite diflindt from the cryftals \, and thus 
it remained till the 19th of January follow- 
ing, when I difcontinued the procefs. Both 
the cryftals and the gold ftill continue not 

I fhall now juft mention my obfervations 
on fome other fubflances expofed to the 
fame heat, though they have nothing in 
them that will be thought of any confe^ 
quence j except that it may be proper to be 
known that the experiments have been 
made, and that no remarkable appearance- 

'Spirit of wine in large tubes underwent 

no alteration, nor did it aiFed the glafs in 

the leail: j but another quantity confined in 

E e a fhort 

41 8 OSfervations en 

a fhort tube, and expofed to much more 
heat, appeared on the 30th of September 
(having been placed in the furnace on the 
1 1 th of the fame month) to have given to 
the infide of the tube, and efpecially to the 
middle part of it, a thin blueifh coating, a 
little inclined to white. Thus it con- 
tinued to the laft, except that the coating 
became more w^hite, and had very nearly, 
if not v^rholly, lofl: its blueifh caft. 

Ether had alfo been confined in a fhort 
and flrong tube on the 1 1 th of Auguft, and 
it continued colourlefs ; but on the 30th of 
September feveral parts of the iniide of the 
tube had a w^hitifh incruftation, the glafs 
being probably affected. Thus it continued 
till the end of the procefs, in January fol- 
lowing, except that I then obferved the 
whitifh incruftation about an inch above 
the furface of the ether, at both ends of the 
tube, owing, I fuppofe, to my hiving, at 
different times, placed both the en^s down- 

With ether I alfo made another expe- 
riment fomewhat fimilar to the above. 


'The EffeBs of continued Heat* 419 
Having filled a glafs tube with it, I poured 
it out again, and immediately fealed it her- 
metically y then holding it in the flame of 
a candle, I obferved a whitiih cloud formed 
in the infide, and when the whole tube 
was expofed to the heat of the fire, and was 
made nearly red hot, part of it became 
whitifh i but the air within the tube was 
not fenfibly changed. 1 made the experi- 
ment in imitation of that with the inflam^ 
mable air, which made the tube becoms 
black; thinking that, if the phlogiftic 
matter had produced that eiFed: in this cafe, 
it might do the fatne in another. 

Olive oil expofed to a very great degree 
of heat, in a ihort andilrong tube, was not 
changed. But in a large tube (owing, I 
imagine, to fome bit of ftraw, or fome 
other fubilance containing phlogifton, 
which, unperceived by me, might be in 
the tube) the oil became, in the interval 
between the nth and the 23d of Auguft, 
quite black, and of the confiflence of trea- 
cle, with a fmell ftrongly empyreumatic 
and oifenfive. I put part pf i^is matter 
£ e 2 into 

42 o Obfervafions on 

into another tube, but it was broke by fome, 
accident, and what remained of the matter 
was as hard as a coal, and quite black. 

Oil of Turpentine, which was quite co-» 
lourlefs, became, in the fame time, quite 
yellow, like dark coloured olive oil. It had 
alfo fome opake particles in it. The glafs 
being fcfftened, it was prefTed inwards. On 
the 9th of Sept. the colour of the general 
mafs was the fame, but there were feveral 
fmall lumps at the bottom, exactly like rolin 
fo appearance. They did not adhere to the 
glafs, but rolled about at the bottom, being 
heavier than the fluid mafs. In a ihort glafs 
tube, alfo, oil of turpentine was a little 

Dijiilled Vinegar fuiFered no change by 
being expofed in a long glafs tube to a com- 
mon fire for about an hour. But common 
vinegar, in the fand furnace, was turned al- 
mofl black in the courfe of three weeks. 
But I afcribe this effed: to fome phlogiftic 
matter contained in it. After the procefs, 
the tafle of it was evidently lefs acid, like 
vapid vinegar, and the air within the tube 


^he EffeBs of continued Heat. 42 1 
was injured ; one meafure of this and one 
of nitrous air occupying the fpace of i .4 

After this I placed diflilled vinegar in the 
fand furnace ; and this, in the interval be- 
tween the 9th and the 30th of September, 
had made a depolit of fome black matter, 
and the tube was coated with it quit-e round, 
at the furface of the liquor. Alfo, in a fhort 
tube, the fame vinegar was a little opaque, 
and there was fome black matter on one iide 
of the tube, half an inch above the furface 
of the fluid. In this ftate thefe tubes con- 
tinued to the laft, when they had depolited 
a brov/nifh fediment. 

Having expofed a fmall quantity of 
water impregnated withjluor acid air, quite 
tranfparent, in a glafs tube hermetically 
fealed, to the heat of a common fire, I ob- 
ferved that, prefently after it began to boil, it 
became of a dull blue colour, and a whitilh 
vapour rofe from it, as high as the middle of 
the tube. Afterwards, the heat increaiing, 
it became tranfparent again, without depofit- 
ing any thing, even when cold» 

E e 3 Repeating 

422 Obfervatlons on 

Repeating the fame procefs, I obferved the 
fame cloudinefs come on after boiling about 
an hour, but after continuing to boil 
two or three hours, it difappeared again. 
This cloudinefs is exadlly like the appearance 
of this impregnated water when fome of the 
fluor cruft is mixed with it. This experi- 
ment, therefore, proves that this liquor, in 
its moll tranfparent ilate, contains a quantity 
of fluor cruft diifolved in it, as I have ob- 
ferved before, in my attempts to account 
for its not freezing, when water irnpreg- 
pated with vitriolic acid air will freeze. 

The effedt of a continued heat on the 'oo- 
latile alkaline liquor v^as much the fame with 
that on the acid impregnations. I expofed, 
in a glafs tube, four feet long, and one third 
of an inch wide, a quantity filling about the 
fpacp of an inch of cauflic fal-ammoniac 
bought at the apothecaries y and in lefs than 
half an hour it became turbid, when over 
the fire. Letting it cool, I foftened the end 
of the tube, and obferved that the glafs was 
prefTed inward§. I then made it boil very 
violently about an hour, during which it 


The EffeSfs of continued Heat, 423 
grew more turbid. When it was cool, I ob- 
ferved that the turbidnefs was occafioned by- 
very fmall white particles, which fublided, 
and left the liquor quite clear at the top. 
Softening the end of the tube again, it was 
driven outwards with great force, and blew 
out the candle; fo that, upon the whole, 
there had been an increafe of elaftic matter 
within the tube, notwithftanding the pre- 

After this, I placed in the fand furnace 
an alkaline liquor of my own preparing, by 
impregnating diftilled water with alkaline 
air. It was confined in a long tube, a quarter 
of an inch in diameter, on the 3d of Sept. 
and on the 9th of the fame month the tube 
was quite coated with a white fubftance, 
and the liquor was turbid, On the 30th of 
the fame month it had depofited a white fe- 
diment, though it was ftill very turbid. 
There was alfo a fimilar incruftation at the 
furface of the liquor, and extending in flreaks 
three inches above it. At the fame time, 
that which had been bought at the apothe- 
cary's, and wjiich had been placed in the ' 
E e 4 fame 

424 Experiments in 

fame furnace exhibited the fame appearance. 
In this the incruftation reached fix inches 
above the furface of the liquor, efpecially 
on the fide to which it had been inclined. 
One of thefe tubes remained in the hot fand 
till the 19th of January following, when I 
found it broken -, five or fix inches of the 
lower part of it being covered with a thick 
white incruftation. 

Common air, which had been confined in 
a glafs tube hermetically fealed, and quite 
covered with hot fand about a week, was 
^ot at all altered in its bulk, or with refped: 
to its property of being diminiihed by ni- 
trous air. 

Several of the obfervations in this volume 
will, I hope, be acceptable to Mr. Delaval, 
and may perhaps be of fome ufe to him in a 
future edition of his excellent treatife on co- 
lours. Among others, the following feems 
to agree with fome of the wonderfully re^ 
gular gradations obferved by him. A fmall 
quantity of \\\& blue folution of copper in 
fal ammoniac, being expofed to the heat of a 

4 common 

Ele^ricity' 425 

common fire, in a long glafs tube her- 
metically fealed, prefently became green, and 
afterwards yellow. 


Experiments in EleStricity, 

THAT conducing power, with refpedf: 
to elediricity, depends upon the vari- 
able flate of fubflances, is evident from a 
variety of experiments. Thus glafs, which 
when cold is a perfed: noncondud:or, is a 
complete conductor in a great degree of 
heat. So alfo, by a contrary procefs, ice, 
Tv^hich when formed in a moderate degree 
of cold is a condud:or, very much like 
water, becomes, as Mr. Achard has dif- 
covered, a nonconductor in a greater degree 
of cold. And I had found that though dry 
wood, and even charcoal, made with the lealt 
poflible degree of heat, is a nonconduftor* 
yet when it has been expofed to more heat, 
it is the moft perfed: of all conductors, not 
exceeded even by the moft perfed: metals 


426 Experiment's in 

themfelves. I have now obferved what, in- 
deed, was not perhaps very difficult to be 
conjedtured, that water, and even quick- 
Jiher in the ilate of vapour, are no con- 
du(flors of electricity. 

Water had been often tried in that kind 
of vapour which is jufl condeniing, in the 
open air J but then it is, in fad:, no other 
than water in very fmall drops ; whereas, to 
try it in the proper form oi Jleam, it muft 
be examined in a degree of heat, in which 
it is incapable of condeniing into water. 
This I did in the following manner : 

I filled a glafs fyphon with water, having 
previoufly put iron wires into each of its 
legs, as is repreiented Fig. 5. and then in- 
verted it,placing each leg in afeparate bafon of 
water, or quickfilver. After this I expofed 
the upper part of the fyphon to a degree of 
hQ.^t capable of converting water Into fleam. 
Then, bringing a charged phial, and mak- 
ing the fyphon part of the circuit, made the 
cxplofion pafs from one wire to the other, 
in the bend of* the fyphon. In this ctife the 
ipark-iieveifiailed %q be asyifible^ as it would 


MeBricity. 427 

have been In the air. The only difference 
was, that in this cafe the fpark was reddifli, 
as it is when taken in inflammable air. I 
could perceive no difference whether the 
heat was greater or lefs, even in the very- 
point of condenfing into water. It is poffible, 
however, that there might be fome red 
difference, though not difcernible in this 
method of examining it. 

In the very fame manner, I made the ex- 
periment in the vapour of quickjihe?', hav- 
ing filled the fyphon with quickfilver, and 
placing the legs of it in bafons of the fame. 
In this cafe, alfo, the electric explofion was 
red; but at one time it was quite vivid. I 
repeated the experiments many times, both 
with water and with quickfilver. 

From thefe experiments, compared with 
fimilar ones that I have made in all the dif- 
ferent kinds of air, I think it may be con- 
cluded univerfally, that all fubftances, in 
this expanded flate of air, or vapour, are 
nonconductors of elediricity. 

There is fomething exceedingly difficult 
to account for in the circumftances in which" 


428 Mifcellaneous 

glafs jars fometimes break fpontaneoufljr 
with eledlrical explolions. In general the 
thinner the glafs is, the more liable it is to 
a fracture in this cafe. I obferved, however, 
in my hijiory of electricity ^ a cafe in 
which a very thick glafs jar broke, in a very 
remarkable manner, by a spontaneous dif- 
charge ; and I have lately obferved another 
hardly lefs remarkable. 

I filled a glafs tube, about three feet long 
and I ^ of an inch wide, the glafs itfelf 
being not lefs than one eighth of an inch 
thick, half full of quickfilver ; and putting 
a loofe coating of tinfoil on the out- 
fide, and beginning to charge it, by means 
of an iron wire connected with the prime 
conducftor, it prefently broke by a fponta- 
neous difcharge, exadtly at the bottom. A 
large piece of the glafs came out, and the 
quickfilver flowed out at the hole. Exa- 
mining it more particularly, it appeared that 
there were a great number of fmall indepen- 
dent fractures, but all very near together -, and 
through ope of them only the charge had 
made its way, pulverizing the glafs, as ufual. 

I then 

Obfervations. 420 

I then charged a long tube of bottle glafs 
in the fame manner ; but this alfo burfl as 
foon, and alfo exadlly at the bottom, 
though not in fo many places. I meant 
to have charged thefe tubes, and to have 
fealed them hermetically, after I had poured 
out^ the quicklilver, in order to obferve 
jaow long fo thick a glafs would retain 
the charge, in purfuance of Mr. Canton's 
firil obfervation of this kind. 


Miscellaneous Experiments. 
I . Of the Colour of Minium, 

AS I was heating a quantity of minium 
in an iron ladle, I was very much 
ftruck with the refemblance of its colour, 
atid of the change of its colour, to that of 
blood. The colour of good minium is, as 
nearly as poffible, that of florid, or what I 
pali, dephlogifticated blood. It is the colour 
they both acquire from expofure to the air. 
When the minium was in the ladle over the 
fire, the furface contijiU'e4 of this colour, 


430 Mlfcellaneous 

but all the lower part of the mafs was of a 
deep red, or black, the colour of dark co- 
loured, or phlogifticated blood. But, like 
blood (only, in this cafe^ the procefs was 
much quicker) the moment that any part of 
it was turned up to the open air, it refumed 
its florid light colour; and when it was 
cold, it could not have been perceived that ' 
any thing had been done to it. However, 
when I expofed a quantity of minium that 
had been treated in this manner to a red heat, 
in a glafs veiTel, though it yielded about the 
fame quantity of dephlogifticated air that I 
imagine it would have done before, it 
yielded much lefs fixed air. 

Imagining that this dark colour might be 
the confequence of the minium receiving 
phlogiilon from the iron, I expofed a quan- 
tity of it to the fame degree of heat in a glafs 
tube, but found the fame change of colour. 
In this, therefore, it refembles the change of 
colour in fpirit of nitre, which is produced. - 
by h©at only, without the help of any addi- 
tional phlogifton, unlefs any may be fuppofed 
to pafs through the glafs. 


Obfervations . 4 ^ ^ 

The tube was feveral feet long, and was 
quite filled with the minium -, and prefently 
after it was expofed to the heat of the fire, 
the colour began to change, growing darker 
and darker continually, till it was almofl: 
black, exadtiy as it had done in the iron 
ladle. But when it was cold, it re-aflumed 
its florid light colour. That it fhould do 
this without the accefs of the external air 
rather furprized me ; and yet that no air, 
except what was contained in, the inter- 
ftices of the minium itfelf, had accefs to 
it was evident from the lower part of the 
glafs being ready to buril with the expan- 
fion of the air, when it was in a melting 

It was obfervable, that from the black 
colour, the minium pafTed, without any 
fenfible interval, into yellow, in which 
ilate it contains little or no air of any kind ; 
fo that the florid colour is an indication of 
its containing pure air, whatever be the 
connexion between thefe circumftances. 
It mufl: be obferved, however, that minium 
deprived of its rfed colour by fpirit of fait 


43 ^ Mifcellaneoui 

does not lofe its property of yielding de-* 

phlogiilicated air. 

«. Of the Mixture of Vitriolic Acid Air, 
and Fluor Acid Air. 

In a former publication, I obferved, that 
when once any two kinds of air are mixed 
together, they do not, at leafl, they do not 
foon, or readily, feparate from each other, 
though their fpeciiic gravities be ever fo 
different, but continue equally mixed 
through the whole mafs. I then made 
the experiment on thofe kinds of air that 
can bear to be confined by water. I would 
now obferve, that the fame is the cafe with 
common air and alkaline, or any of the 
acid airs. For though all thefe kinds of 
air differ in fpecific gravity from com- 
mon air, yet if they be mixed with com- 
mon air, and water be admitted to them, 
the quantity will decreafe more or lefs 
ilowly in proportion to the quantity of 
common air in the mixture. Whereas, if 
the alkaline or acid airs had been heavier 
than the common air (as the latter, at leafl, 


Obfervatkns, 4 j ^ 

inanifeflly are) and did not mix with it, 
the water would abforb them as readily as 
it does when the jar contains no other kind 
of air ; as, on the other hand, if the com- 
mon air had been the heavier, it would 
have protefted them from the accefs of the 
water, which would not, in this cafe, be 
able to come at the acid or alkaline air, and 
therefore could not abforb any part of the 
quantity. I have noted, however, one excep- 
tion to this rule refpe(5ting alkaline and 
inflammable air, which did not feem to 
mix together. See Vol. I. p. 176. 

I have fince made a mixture of vitriolic 
acid air and fluor acid air, and find that 
they continue intermixed throughout. I 
mixed equal quantities of them in a jar of 
quickfilver, and obferved, that when water 
was admitted to the whole mafs, the cruft 
was formed equably from the bottom to 
the top of the velTel. 

3. Of Fluor Acid Air corroding Glafs, 
Fluor acid air, when it is firft produced, 
corrodes the glafs veiTel in which it is 
F f generated. 

434 Mifcellaneous 

generated. But whether it did this of itfelf, 
merely in confequence of being heated, or 
whether the moifture, or fomething elfe 
contained in the oil of vitriol, by means of 
which it is formed, contributed to this 
effed, did not certainly appear. When 
this air is cold, it does not at all affedt the 
glafs veiTel in which it is confined. In 
my late attempts to confine the different 
kinds of air in glafs tubes hermetically 
fealed, in order to expofe them to a con- 
tinued heat, I obferved that it is limply 
the heated air that has this eifed. For 
when I had filled a tube with this kind of 
air, and was endeavouring to take off dif- 
ferent lengths of it, with a blow pipe, I 
found that, when the glafs became red hot, 
it was always fo corroded, and dilTolved, 
that it was impofiible to clofe it by fealing. 

4. Common Air affeSied by heated ^lickfiher. 

In a former publication I brought fome. 
arguments to fliow that there is no air in 
quickfilver ; as has generally been imagined, 
and that all the air which is difcovered in 


Obfervathns, 4^5 

toiling it in a glaib tube, is only that 
which had been concealed, and comprefled, 
between the quickfilver and the glafs. 
Having then colleded a fmall quantity of 
this air, I obferved that I found it to be 
common air, being diminilhed by nitrous, 
«ir. But the quantity being fmall, and 
not having applied a very accurate meafure, 
2 have fince repeated that experiment v/ith 
more precaution, and find fuch air to be 
in fome degree phlogifticated -, but this, I 
imagine, arifes, from the phlogifton efcaping 
from the . quickfilver, efpecially when it 
15 .hot, 

I firft filled a tall thin tube, about a^i 
inch in. diameter, with quickfilver; and, 
^xpofing the upper part of it to a degree of 
heat that converted it into vapour, in the 
manner reprefented Fig. 4. and confe- 
quently efFedtually fetting at liberty all the 
mx that was confined between the quick* 
filver and the glafs, I colleded and ex- 
aniined that air, and found it not to be 
dimiaiifhed by nitrous fo much as com- 
gcnon air is, . - • 

'Viz I then 

436 Mifcellaneou's 

I then repeated the experiment by throw- 
up a quantity of common air, and cxpofmg 
it to heat mixed with the vapour of quick- 
filver, and let it continue in that ftate four 
br five hours. After tliis I perceived that 
the air vv^as confiderably diminiihed in bulk ; 
and, examining it, I found that one mea- 
fure of it and one of nitrous air occupied 
the fpace of 1.66 meafures. The air, 
therefore, in the former experiment, not 
having been pure air, is no proof of its 
having been incorporated with the quick- 
filver ; iince common air mixed with it, in 
the ftate of vapour, receives phlogiiion 
from it. This proves that, like other 
nnetals, quickfilver is difpofed to part witH 
phlogifton to the air when it is hot. Query, 
what becomes of the calx of mercury to 
which the difcharged phlogifton belonged ? 

4. Of the Mixture of the Vitriolic and 
the Nitrous Acids, 

Becaufe a mixture of nitrous acid will 
difcharge the black colour from phlogifti- 
cated vitriolic acid, Mr. Beaume infers 


Obfervations, 4^7 

ihat the former has a ftronger affinity with 
phlogiflon than the latter. He alfo obferves 
of this mixture that it will readily inflame 
oil of turpentine, but that nothing farther 
is known concerning it. 

I would obferve, however, that the vitrio- 
lic acid does likewife difcharge all colour 
from the nitrous acid, and therefore, reafon- 
ing as Mr. Beaume doe??, we might draw a 
conclufion the reverfe" of his. I would 
therefore rather fay, that the two acids in 
conjundion have a different adlion upon 
phlogiflon than they have when feparate. 

If the marine acid be mixed with the 
vitriolic, the marine acid air is inflantly ex- 
pelled and the water is, I fuppofe, feized by 
the acid of vitriol. But when the vi-v 
triolic and nitrous acids are mixed, no fuch 
cffedt takes place. They, therefore, feeni to 
occupy the water jointly, without either of 
them diflodging the other, at leafl in the 
fpace of fome weeks. What more time 
will effecft I haye not yet feen. 

If the nitrous acid be poured gently 

upon the vitriolic, ftrongly concentrated, 

F f 3 they 

43 B Mifcellanebus 

they will continue unmixed for forne time ; 
but, without any agitation, they will ineor^ 
porate gradually, a white cloudinefs being 
alvyays feen where they are contiguous. 
When they are fhaken together a fmall de- 
gree of heat will be produced, and numberlefa 
bubbles will be formed, which, however, are 
prefently abforbed. There is alfo at fir ft a 
whitifh vapour over the furface of the mix- 
ture ; and after feme time, though both the 
acids be ever fo pure, and the vitriolic has 
been diftilled again and again, there will be 
a depofit of a white fubffcance, which I have 
not yet examined. 

I have obferved that the yellow colour of 
the common fpirit of nitre is difcharged by 
a mixture of the vitriolic acid. When I 
poured a weak green fpirit of nitre upon 
concentrated oil of vitriol, it became yellow 
where they were contiguous ; but the quan-*- 
tity of nitrous acid being much greater than 
that of the vitriolic, it was green above^ 
without any vifible vapour on its furface. 
The next morning the nitrous acid was 


Ohfervathns^ 43^ 

colourlefs, contiguous to the vitriolic, and 
the reft yellow. 

Afterwards I poured upon concentrated oil 
of vitriol an equal quantity of that nitrous 
acid, which had firft acquired a deep orange 
colour by heat, . and then had become green 
by keeping. The eiFedt was, that from green 
it inftantly became yellow throughout, and 
continued diftind from the vitriolic acid fix 
days. In one day they did not feem to afFe<a 
each other in the leaft, but afterwards a 
cloudinefs was obferved, where they were 
contiguous to each other, which increafed till 
almoft the whole had that appearance ; and 
when they were ihaken together it was 
tranfparent like water. 

In order to try the full power of the vu 
triolic acid to difcharge the colour of fpirit 
of nitre, I diffolved in the ftrongeft fpirit of 
nitre a quantity of copper, which gave it a 
deep green colour. But on mixing it with 
vitriolic acid it inftantly became perfectly 
colourlefs, and the copper was precipitated 
in the fprm of a white powder, 

F f 4 - I poured 

440 Mifcellaneoiis 

I pourecl very gently a quantity of aqua 
regia, made by impregnating marine acid 
with nitrous vapour, on vitriolic acid, and 
at lirftit eiFervefced very much, and thelow^er 
part w^as of a turbid white, while the upper 
part retained its orange colour. After fbme 
time the mixture was of a light orange 
throughout. I have not yet rnade any farther 
obfervations upon it. 

To try how flrongly the nitrous acid va-r 

pour was retained in this mixture'of the two 

acids, I expofed a part of the mixture to the 

heat of a common fire, in a long green glaft 

tube hermetically fealed, and found that 

though I kept it boiling, it continued colour-f 

lefs a- confiderable time. Afterwards a red 

vapour was expelled from the mixture, and 

at length the whole tube was filled v^ith it. 

But when it was cold the vapour was* all 

abforbed again, and the mixture, which 

was then of a pale orange colour, became 

afterwards quite colourlefs, as at firft. This 

is not the cafe with oil of vitriol impregnated 

v/ith nitrous vapour. For this vapour 


Chfermthm, 441^ 

cfcapes from it even without heat, and much 
^ore with it, and it is not re-abforbed. 

^. Of a Solution of Copper in Jlrong nitrous 

It is feme thing remarkable that though a 
great quantity of nitrous air is produced by 
the folution of copper in a diluted nitrous 
^cid, no air at all is procured by a folution 
of the fame metal in the ftrong acid. There 
i§ not even any appearance of air being 
formed, and afterwards abforbed by the 
^cid, as in the limilar folution of mercury. 

paving fatu rated a quantity of ftrong fpirit 
of nitre with copper, of which it dilTolves 
but a frhall quantity, I diflilled it in a 
green gjafs retort. The firft part of the acid 
that came over was orange coloured, from 
being of a deep green; but the laft was 
quite tranfparent and weak. ISTo air, that I 
^ould perceive, was produced, but a tubu- 
lated receiver being made ufe of, a fmall 
^^uantity could not be difcovered, 


^4-2 Mifcellaneous 

6. Of Atr from Minium y dijblved in Spirit 
of Salt* 

Spirit of fait, I, have obferved, diffolves a 
great quantity of minium. In order to dif- 
coyer what became of the dephlogifticated 
air it contains, I diftilled a quantity of that 
folution, which was of a yellow colour, 
made by the firft afFufion of the acid. When 
the folution became hot it yielded a quantity 
of dephlogifticated air, mixed with a very 
fmall quantity of fixed airj fo as to make 
lime water turbid only in the flighteil de- 
gree. As it boiled no air at all was procured^ 
nor when it was diftilled to drynefs. 

I treated in the fame manner a faturated 
folution of white minium, made fo by its 
colour having been difcharged by a previous 
affufion of the acid. But this folution 
yielded no air at all from the beginning to 
the end of the procefs. Nor was the com- 
mon air in the retort phlogiflicated either at 
the beginning or the end. 

J, Ex-*- 

Obfervationu 443 

7. Experiments with Frofl, 

I have obferved. Vol. III. p. 360, that 
Water impregnated with vitriolic acid air 
calily freezes, retaining all its air, which is 
a pretty extraordinary fad; being the reverie, 
in one refped:, of water impregnated with 
marine acid air, which cannot freeze; and, 
in another refpedt, of water impregnated with 
fixed air, which in freezing parts with its 
air. At the fame time I obferved that water 
impregnated with fluor acid air did not 
freeze. I now find that the latter fiuid 
does freeze, though it requires a greater de- 
gree of cold than water impregnated witli 
vitriolic acid air. The latter effed: I attri^ 
buted to the prefence of fome of the fluor 
cruft in the folution, and I think this con- 
jedureis, in fome meafure, confirmed by the 
following obfervations ; in which it will be 
feen, that lime water did not freeze fo foonas 
common water, and that lime water impreg- 
nated with vitriolic acid air did not freeze 
fo foon as common water fo impregnated. 

5 Jan. 

' 1.44 Mifcellaneous 

Jan. 7, 1779. I expofed to the cold all 
night a phial of pump water, and one of the 
fanje water faturated with quick lime. The 
next morning I found the thermometer at 
28, the pump water frozen folid, but the 
lime water not frozen at all. 

Jan. 9. When the thermometer was at 
leafl: 23 water impregnated with fluor acid 
air, after being expofed to the cold all night, 
was imperfedily frozen. At the fame time 
water impregnated with vitriolic acid air was 
quite folid, and alfo a quantity of the fame 
in which fome chalk had been dilTolved. But 
lime water impregnated with vitriolic acid 
^ir was quite fluid. Lime water was frozen, 
and a little of the lime was precipitated. 

Jan. 12. "When the thermometer was at 
20, and had probably been lower in the 
pight, I found the lime water impregnated 
with vitriolic acid air, and alfo the water 
impregnated v^ith fluor acid air, folid 
throughout. The former was quite white, 
Jput was tranfparent again when the ice 
melted. As the ice of the fluor acid melted, 
it fwain on the furface of the liquid part. 
'-' ■■- - 8. Op 

Ohfewattons, 44^ 

8. Of a Valine Subjiance formed by Earth oj 
Alum and fxed Air. 

At the time that I firft heard of Mr. 
Achard's capital difcovery of the formation 
of cryftals from various earthy fubflances 
and fixed air, I endeavoured to fimplify his 
procefs (which requires a good deal of at- 
tention, as well as an expenfive apparatus, 
and of difficult conftru(5tion) and among 
other things I fully faturated with earth of 
alum a quantity of water, impregnated with 
fixed air, and I let an ounce phial of it, with 
a redundancy of earth of alum in it, remain 
fome months, in v/hich time a great part 01- 
the water was evaporated. But after that 
time I found in the fediment a faline fub- 
fance, confifling of two cones, on the fame 
bafe, each having fix fides, and the whole 
Weighing five or fix gr;;iins. It had a peculiar 
tafte, fomething lijce that of alum. Having 
had it in my mouth feveral times before I 
thought of weighing it, I cannot be quite 
certain what its original weight was. I had 
flattered riiyfelf with the expedation of 

a dif- 

44^ Mifcellaneoui 

a different kind of fubftance from this 


9. Remarks on the Article Gas in the new 
Edition of Mr, Macquer'j DiSfionary 
of Chemijiry, 

That excellent chemift, and moft per- 
fpicuous of writers, Mr. Macquer, has, in 
a new edition of his valuable DiBionary^ 
given a large article on the fubjed: of the 
different kinds of air, under the article gas^ 
which I think very judicious, and ufeful in 
moft refpefts, as well as highly flattering to 
myfelf. But as he feems to me to have made 
a few miftakes, I think I ihall objiige him, 
and others, by endeavouring briefly to p(^nt 
them out. 

He agrees with Mr. Lavoifier in fup* 
pofing that phlogifton, combined with com^ 
mon air, converts it into fixed air, p. 260, 
292, &c. and he imagines, that I fuppofe^ 
air to be injured by a mixture of fixed air, 
and that plants reftore noxious air by im- 
bibing that fixed air, p. 293. Agreeably to 
this idea, which runs through the whole 


Obfervations, ^'t 

article, he fays, that the agitation of fixed air 
in water makes it approach to the nature of 
wholefome air, p. 254, and that a mixture 
of nitrous air with common air converts it 
inta fixed air. He even exprefsly fays, 
p. 297, that the union of phlogifton with air 
diminifiies its quantity, increafes its fpecific 
gravity, renders it unfit for refpiration 
or combuftion, and makes it approach to 
the nature of fixed air, by pafiing through 
the ftate of phlogifticated air. 

On this fubjeft, however, this ingenious 
writer does not give my opinion, or one that is 
agreeable to fad:.. For air fimply injured by 
phlogifton is not heavier, but lighter thaa 
common air^ and not making lime water 
turbid, or being peculiarly liable to be 
abforbed by water, it fhews no fign pf ap- 
proaching to the nature of fixed air, which 
is, moreover, heavier than common air; not 
YfiW any length of time, or addition of more^ 
phlogifton, tend, in the leaft, that I know, 
to bring it to this ftate. 

On the contrary, it will rather follow 
from my obfervatipns, that fixed air is con- 

44§ Mifcellaneous 

vertible into phlogifticated air, and this inta 
pure air, by more procefles than one, and 
eipecially by incorporating with water, by 
which a portion of any quantity of fixed air 
is converted into phlogifticated air. Confe- 
quently, by repeating the procefs, the whole 
would become fo ; and phlogifticated air is 
by various procefles convertible into pure air. 
So that fixed air may rather be called the 
medium between pure air and phlogifticated 
air, arM not phlogifticated air the medium 
between pure air and fixed air. 

He aflerts, with Mr. Lavoifier, p. 298", 
that metalic calces with the addition of 
coEribuftible fubftances, yield fixed air, a 
miftake on which I have animadverted 

He mentions, p. 377, the vegetable acid 
air as my difcovery. But though I have a 
fcd:ion on that fubjeft. Vol. II. p. 23, I 
obferved in the fame volume, p, 334, that, 
not having been able to get any air front 
radical vinegar, and finding that vitriolic 
acid had been employed in making the con- 
centrated vinegar from which I had extracted 


Ohferuations, ij.^^ 

that air, the properties of which I had de- 
scribed under the title above-mentioned, I 
concluded that it was, in fad, the vitriolic 
acid air, though perhaps a little modified ; 
and that, prbperly fpeaking, there is no fuch 
thing as a vegetable acid air. 

He fays, p. 313, that I fpeak of fixed air 
as not leiTening the inflammability of in- 
sflammable air, the contrary of which he 
had himfelf obferved. What I have faid is, 
that when fixed air and inflammable air 
hrave been mixed together, water will abforb 
the fixed air, and leave the inflammable air 
pofleiTed of its original properties. Inflam- 
mable air itfelf, I obferve, will extinguifh a 
red hot coal, and that it cannot be ienited 
with a candle, but by the help of common 
air, as in its iSuing out of the mouth of a 

Q g SEC- 

45^ Supplemental 


'Experiments and Obfervations made Jince the 
preceding Sections were fent to the Prefs* 

§ I. Of Oil of Vitriol impregnated with 
nitrous Vapour. 

I HAVE defcribed a number of beautiful 
feather-like cryjials formed in fome phials 
containing oil of vitriol impregnated with 
nitrous vapour. Cryflals limilar to thefe 
may be produced at pleafure, if the vitriolic 
acid be highly concentrated, and the nitrous 
vapour very copious; but they will appear 
on the fides of the phial, and not in the body 
of the acid itfelf. 

When the vitriolic acid is nearly fatufated 
vi^ith the nitrous vapour, hold the phial 
(wrhich fhould be a large one, containing 
about a quart) and turn it fo as to moiilen 
all the infide of it. Then immediately throw 
in a very copious nitrous vapour, fo that the 
whole phial Ihall be intenfely red, and run- 
ning over ^ after which put in theflopper,and 


Ohfervationi. 4 r i 

let it remain quite Hill. The upper part of 
the oil of vitriol will then be of an orange 
colour, and all the lides of the phial, and 
cfpecially the parts towards the bottom, will 
foonbe quite covered with thofe cryftals, 
b^t of different lizes. By degrees they will 
be formed on the furface of the acid y but 
in a few hours afterwards, when the nitrous 
vapour is equally diftributed through the 
body of the oil of vitriol, all thefe cryftals 
will difappear. 

By repeating this procel^, one half of the 
whole body of vitriolic acid will be cryftal- 
lized in an irregular manner, as if it was 
congealed. When I have poured the whole 
of this femi-congealed mafs into a fmaller 
phial, juft large enough to contain it, the 
coagulated part has fubfided to the bottom, 
and other (^ryflals have gradually fotmed, 
fhooting with fome regularity from it into 
the middle of the fuperincumbent liquid, 
which has always ' become more pellucid, 
and approached more to the colour of fpirit 
of Jiitre, in proportion as the cryftals have 
extended themfelves. 

G g 2 Finding 

452. Supplemental 

Finding th^t all the acid of vitriol was 
contained in the cryftals, and that the fuper- 
incumbent liquid became in time pure fpirit 
of nitre, I was delirous of knowing whether, 
if there fliould be any phlogiftic mattec; 
previoufly contained in tii$ oil of vitriol,, 
the phlogifton would be retained in th^: 
cryflals, or pafs. into the fpirit of nitre. 

With this view I dilfolved a fmall quan- 
tity of bees- wax in highly concentrated oil 
of vitriol, making it thoroughly black, and, 
greatly increa?fing its vifcidity,- and afterwaEds 
I impregnated it with nitrous vapour, and, 
Ihut it clofe up in a fmall phial. After fome 
weeks the cryftals began to form, and they, 
were intirely white, juft as if the vitriolic 
acid had been pure. The procefs is not yet 
completed ; but I expedt that the nitrous 
acid will be highly phlogiflicated. Does- 
no t this experiment feem to prove, that the 
nitrous acid has a ftronger affinity with* 
phlogifton than the vitriolic ? The fad: is 
certainly a pretty remarkable one. 

Obferijations, 4j^ 

§ 2. Of the Colour of the nitrous Acid, 

I have obferved that heat never fails to 
give a high orange colour to the paleft 
fpirit of nitre, and that with the lefs heat 
the acid is made, the lighter the colour of 
it will be. Having purpofely made the pro- 
cefs for difliiling this acid with as little heat 
as poffible, and taking care to have no 
phlogiftic matter m the materials, I procured 
a large quantity of the acid (that which 
came in the middle of the diftillation) as 
nearly as poffible quite colourlefs, like 
water, and yet of the ilrongeft fort. 

I have alfo obferved a farther, and a very 
remarkable change of colour in the phlo- 
gifticated nitrous acid, after being kept a 
long time in phials with good glafs ftoppers. 
For from being of the deepefl; orange, it has 
become quite green, the fuperincumbent 
vapour continuing ftill of an orange colour. 

This change I iirft obferved in a confider- 

able quantity of nitrous acid which had 

been of a light ftraw colour, and had alTumed 

|j;i? deepeft orange, by expofure to heat in a 

G g 3 glafs 

454 Supplemental 

glafs tube hermetically fealed. This was 
alfo the cafe with feveral quantities of the 
acid incumbent on the cryllals of oil of 
vitriol, of which I have made frequent 
mention ; and in one of the phials it had 
palTed from green to a deep blue. 

I mufi: alfo take notice, in illuftration of 
this fad, that, in the procefs for producing 
the nitrous vapotir, viz. the r?pid folution 
of bifmuth, the liquid that comes over, 
mixed with the vapour, and which drops 
now and then from the end of the tube out 
of which the vapour ilTues, is generally of a 
deep blue. 

Lailly, if a quantity of this deep green 
acid be put into a large phial, where the 
vapour has liberty to expand itlelf, it re- 
fumes its orange colour. This I have alfo 
obferved is the cafe on pouring it on con- 
centrated vitriolic acid. 

§ 3 . Of nitrous Air imbibed by Charcoal. 

I dropped a piece of red hot charcoal into 
a phial of nitrous air, and immediately in- 
verting it in a bafon of mercury, the air 


Obfervations, 4^5^ 

was prefently reducedT to one fifth of the 
whole. Thus it continued two months, 
without any femible change ; after which 
I found that the air that remained uh- 
abforbed did not afFed common air, nor did. 
the air that was emitted by the charcoal, 
when it was plunged in water > fo that,in both 
thefe cafes, the air feems to be intirely 
deprived of its peculiar properties, and to 
become mere phlogifticated air. 

§ 4. Of nitrous air being, to Appearance, 
converted into Injiammabk Air, 

I have mentioned a cafe. Vol. I. p. 217, 
in which nitrous air, after having been 
expofed to iron, became not only partially 
inflammable, admitting a candle to burn in 
it with an enlarged flame, but was even 
fired with an explofion, like inflammable 
air from metals by oil of vitriol. I have 
fince met with a more remarkable fad:' of 
the kind. 

At the latter end of September 1778, I 
had put a pot of iron filings and brimilone 
into a jar of nitrous air, which, in the courfe 

G g 4 of 

45^ Supplemental 

of feveral days, was dirniniflied by it i|i the 
ufual proportion. From that time till the 
beginning of December it had continued 
without any change that I had perceived j 
but about that time, imagining it was in- 
creafed in bulk, I tobk exad: notice of the 
dimenlions of it, and prefently found that 
the quantity was certainly increaling. Upon 
the whole, I concluded that it hadincreafed 
about one fixth of its bulk, from the itate 
of its greateft diminution. On the iitl:^ 
of December I examined it, and found it 
to be proper inflammable air, being fired 
with many explofions when tried in the 
ufual manner, but they were ' not fo 
vigorous as thofe with frefli made inflam- 
mable air from iron and oil of vitriol. 

After this, on the 12th of December, 
I put a pot of iron filings and brimflone to 
another quantity of nitrous air, and on the 
4th of February following it had increafed 
in bulk about one third, and then burned 
with explofions like the former. But a quan- 
tity of nitrous air expofed to the effluvium 
of liver of fulphur, the very fiune time, 


Obfervations, 4^7 

never increafed at all after the period of its 
utmoft diminution, and was mere phlor 
gifticated air. 

The circumilance that makes it' rather 
probable that here was a converlion of 
nitrous air into inflammable, is that I have 
never found air of any kind to come from 
this mixture of iron filings and brimftone, 
except in a confiderable degree of heat; 
and to give it what I thought a fair trial, I 
confined it at one time underwater. Vol. I. 
p. 108. But I never kept it in thofe cir- 
cumftances more than a week or a fortnight. 
Perhaps more time may produce the fame 
CjfFect as heaty and thus a quantity of in- 
flammable air may be added to the phlo- 
gifl:icated refiduum of the decompofed 
nitrous air. But then the explofions 
feemed to be rather too vigorous for that 
proportion of inflammable air in the phlo- 
gifl:icated air. 

To try whether, after the ufual diminu- 
tion of common air by this procefs, there 
would, in length of time, be a generation of 
inflammable air, I put a large pot* of iron 
5 filings 

45 S Supplemejt tal 

filings and brimilone into a fmall quantity 
of conimon air, and an the 4th of February 
following, when I was obliged to put, an 
end to the experiment (but it was the fame 
iime in which the nitrous air had become 
inflammable) though there was an increafe 
qf about one twelfth from the ftate of its 
greateft diminution, there was nothing fen- 
iibly:inflammable in_ it. It was mere phlo-. 
gifticated air. What will be the effe^ft of 
more time with this procefs I cannot tell, 
and therefore I do by no. means determine 
whether the nitrous air was changed intp 
inflammable air; or whether, being iirft 
deconipofed, and become phlogidicated air, 
there was an addition of inflammable air 
made to it. 

'^^yOf the different EffeBs of Liver of Sul- 
phur, and Flowers of Zinc on coloured 
Spirit of Salt 

Both liver of fulphur and flowers of 

zinc, I have obferved, difcharge the colour 

of fpirit of fait. But when I difcharged 

the colgur of a quantity of this, acid, made 

2 very 

Ohfer'uattons, 459 

very yellow with various impregnations, 
with liver of fulphur, it recovered its colour 
by being expofed to the open air. On the 
contrary, though flowers of zinc produced 
the farae effecSt, in discharging the colour 
of another portion of the lame acid, the 
coloair did not return by expofure to the 
air, not even though liver of iulphur was 
afterwards put to it. 

§ 6. Of the ^ffe5i of Marine Acid Air ok 
Flowers of Zinc, &c. 

Being defirous of afcertaining whether the 
marine acid dr would combine with the 
fame fubftances that the marine acid dif- 
folved, I made the trial with the flowers of 
zinc and red lead 5 arkd found that both thefc 
fubflances abforbed a very great quantity 
pf that air. I therefore conclude that 
whether the marine acid be combined with 
water, or not, it has the fame affinity with 
thefe earthy fubflances. 





A Letter /^-om' Sir Williau- Lee, Baronet^ to Dr. 
Priestley, en the Ufe of Water impregnated -i^it^ 
fixed Jir, in preferving Flejh Meat from FutrefaSlion, 

YOUR benevolence will, I am fure, excufe the pre- 
fent trouble I give you, however intruflve and 
otherwife unwarranted, as it proceeds from a like difpo- 
fition, and is occafioned by your own experiments foi 
jUdicioufly directed to the fervice of the public. 

The uncommon difficulty of keeping meat in this hot 
-feafon, led me to make trial of water impregnated with 
fixed air to preferve it from putrefaction ; and I can afllire 
you from repeated trials, that in my own family, and in 
a neighbour's alfo, we have been enabled to preferve meat, 
as- perfectly fweet and good to the extent often days, as 
at the firft killing, and there feems no doubt it might be 
preferved much longer. I made'ufe of Mr, Parker's ap- 
paratus and directions, but repeated the vitriol and chalky 
after four or five hours ftariding, to the fame water; which 
impregnated it much ftronger than one operation could 
do. With this water our houfekeeper wafhed the meat 
two or three times a day, and has even recovered fome 
meat that had begun to change. It feems to me too im- 
p6rtant a faft to be paffed over, and that to make it moft 
bieneficial to the puljiick it ought to, be in your hands, 

' " wh*- 

462 The APPENDIX. 

who will beft know how moil efFs<Sl:ualIy to direct it td 
that purpofe, if yoii think any material one may be 

I am. Sir,. 

Your very humble fervarit, 

Hartwell, W. Lee. 

July 19, 1778* " T 

P. S. It gives no tafte to the meat, and we now con-* 
fiaritly ufe it to all that comes into the houfe. 


ExtraSf of a fecond Letter from Sir WiLtrAM Lee on the 
fame Suhj^SI, and alfo on the Vfe of fuch Water in puiri^ 
■ Feven, 

,,: Sir, 

I have to add, in confirmation of what I wrote you, 
that I gave quantities of the water, fo impregnated, to 
feveral people in thjs, neighbourhood, and alfo an appa- 
ratus, and necefiary inftru61ions, to a perfon in the next 
adjacent market town, in order to fpread the ufe thereof 
as fpeedily as poflible ; and I have had concurrent tefti- 
mony from all but one fingle perfon, whofe fervants I 
apprehend had not given it fair play, confirming the effi- 
cacy ^(f the method. Particularly, a butcher, who deals 
pretty largely, affures me, he faund the greateft fuccefs 
from it, and only objedls th^t the veal vi^as a little dif- 
coloured, though kept perfeflly fweet ; and the perfon to 
whom I gave the apparatus thinks it will prove of great 
advantage, from the fuccefs of thofe ta whom fhe has fold 


The appendix. ^j 

th« water. I can further add, partly from my own ex- 
perience, and from the teftimony of my houfekeeper and 
femily, that not a morfel of flefh or fifh treated in this 
*manfter, fuffeted the whole feafon after, except one piece 
of veal which {he purpofely fufFered to become green in 
order to try the utmoft force of the water, for (he was fo 
pleafed, and prejudiced with the efFedl-s ftie had feen, that 
I believe Ihe thought it capable of reftoring any thing, 
though ever fo putrid. The event in this cafe was, that it 
fo far reftored it to colour and fmell that (he drefled it, 
as perfe^ly good j but I muft own to you, that I found it 
not eatable, from its exceflive tendernefs and very vapict 
flavbtir. * 

What led me to the trial in the firft inftance of this re- 
medy was the juil grounds I had to believe, as I thought, 
that fixed air liad been of confiderabte benefit in a 
poor family, I had relieved and afSfted in a violent putrid 
fever and fore throat. The father had it in the moft vio- 
lent degree, fo as to be given ovcrby the apothecary, and 
was thought not able to live 24 hours j but by vigoroufly 
perfifting in Dr. Fordyce's method he. recovered, though 
to all appearanqe he muft have floughed through the in- 
teftinal canal. Some weeks after he relapfed as bad ac^ain 
as ever, and the wife and a child at the breaft began to 
complain, and had fome fpecks in the throat, upon 
which, after cleanfing the houfe as well as poffible with 
vinegar and water, a velfel of the fermenting ingredients 
was kept eonftantly at work, in the room where they fat 
and lay, the man fumigated his throat v/ith tjie air, by 
means of a proper pipe, and returned to the before-men- 
tioned plan of Dr. Fordyce's, the woman and child drank 
only ftrong chamomile tea about three times a day, and 
through the bleffing of Providence all recovered perfedly, 
and have had no return ever fince, now more that? two 
years pad. 


46+ The appendix. 

Thus, Sir, I have given you as fall and exa£l a nar- 
rative as poifible of fimple fads, from which I doubt not 
you vi^ill draw feme practical advantage to the publick, 
more than my fphere of life will admit, which was my, 
inducement to intrude upon your time ; and very happy 
Ihall I be to receive any commands from you, wherein I 
can in any fort render myfelf ufeful by any further invefti- 
gation of this fubje6l, and 

am, Sir, 

Your obedient humble iervant, 

W. Lee, 


jf Letter from Mr. Adam Walker, LeSfurer In Na^' 
tural Philofophy, to Dr. Priestley, on the JppUcatiojt 
ef fixed Air to an inflamed ^reajf. 

Hampton Court, 6th Gdtober. 
Dear Sir, 

I have lately feen fuch an efFe£t from a topical applica- 
tion of hxed air, that I cannot deny myfelf the pleafure of 
communicating it to you. 

My wife lay in about fix months ago ; and as fhe nurfes 
her children, was very much diftrefled with fore breafts : 
Ihe had the advice of the do6lors and good women of the 
neighbourhood, and I fhall give their prefcriptions^ and ; 
their effects in (he order in which they were applied. The 
inflammation was at leaft four inches in diameter. 

The firfl was a fere cloth of bees wax and mutton fuet» 
which foftened the inflamed part, but rather added to the 

2d, A 

The appendix. 465 

fid, A folution of alum in rum, rubbed on the part with 
a feather. — 7 his aflringent cracked the whole, and en- 
cruftcd it in fuch a manner that the pain was intolerable, 
and the inflammation increafed. 

3d, The jelly like matter produced by hot water being 
poured on quince pippins- Had no effect. 

4th, Powdered i -pis calaminaris, dried and encrufted 
the part ; and the inflammarion grew ftill worfe. 

5th, The oil of egg applied fix weeks, only foftened, 
did not ftop che increafmg infiammation. 
6th, Fuller's earth increafed the inflammation. 
7th, A mucilage of gum arabic in Hungary water, 
alfo increafed the malady. 

8th, Beeswax and oil, did neither good nor harm. 
9th, Spermaceti ointment, ditto. 

loth, Bread poultices produced many red fpots round 
the nipple, and increafed the inflammation, 
jith. Camphor ointment, ditto. 

Thefe having been applied for the fpace of four months, 
and the inflammation growing worfe and worfe, fhe was 
prevailed upon not to perfevere in nurfmg the child. 
However, as I had often recommended an outward appli- 
cation of fixed air, (he would rather try this than wean the 
child ; fo I fitted up an apparatus in fuch a manner that 
the fixed air difcharged from chalk by oil of vitriol, ifiiied 
from the phial containing thefe materials through a glafs 
funnel large enough to cover the inflamed part of the 

This funnel was held fo faft to the breaft, that no air 
could efcape , but when by its increafe, it preffed too 
hard upon the breaft, a little was let out. She held it to 
the part about half an hour at a time, twice a day, and 
from the firft application it loft its livid appearance: in 
four days the child fucked without giving pain; and in 

H h ten 

466 The A P P E N D I X. 

ten days the cure was completed^ and no return of the in* 
iflammation fince, being upwards of two months, and the 
child is yet un weaned. 1 am, 
Dear Sir, 

Yoursj Szc. 

A. Walker. 


jf Letter from Mr. Becket, Bookfeller in Brljiol, on the 
Air extra6iecl from the Water of the Hot-well^ and on the 
Mr of that City and the Neighbourhood. 

Briftol, 20th Oaober, 1778. 
Dear Sir, 
When I had the pleafure of feeing you laft, you ex- 
preflTed to me your defire of being informed of the nature 
and quality of the air, contained in the water of the Hot- 
well, near this place.— Want of leifure obliged me to de- 
fer making the proper .experiments till a few days ago; 
the refult of which was as follows :— Having made a 
quantity of this water acquire a boiling heat in a long 
curved-neck retort, which was quite filled, and the orifice 
immerged in water, the air was caught in the upper part 
of the beiid, and all extraneous air entirely excluded. 
After putting it into the air gage, I firft of all applied to it 
your teft of the nitrous air, by which it appeared to be a 
very pure common air, fo far dephlogifticated, as to take 
exa6i:ly an equal quantity of nitrous air before it increafed 
In bulk. I repeated the experiment feveral times, varying 


The appendix. 467 

the opera' ion and quantity of air, but with the fame re- 
fult. At the fame time I alfo tried the air of other kinds 
of water. The air of rain water, which had ftood in a 
ciftern, was not fo pure, and but little different from 
common air j but that which came from the water of a 
conftant and good fpring, the refervoir of which is in the 
flreet in which I live, was nearly the fame as that of the 
Hot-well water. I could not difcern any appearance of 
fixed air in it. After it had ftood two days in the 
gage-tube, with water, the quantity did not appear dimi^ 
nifhed, nor did it render lime-water turbid. As a farther 
proof, however, of its being really dephlogiflicated, a 
candle would burn in it with fuperior luftre to common 
air ; and when fired with inflammable air, the explofion 
was confiderably louder. 

I have at times, as opportunity permitted, made fre- 
quent ufe of your excellent teft of the purity of common 
air, by means of nitrous air. I have taken confiderable pains 
in order to prove its accuracy, by mixing together different 
kinds of common and noxious air, in different proportions ; 
and have frequently been much pleafed in obferving the 
correct lengths, which thefe columns of air would occupy 
in the gage-tube, agreeably to what I apprehended they 
ought to occupy from a calculation of their proportions. 

I have generally found that the air in this city, and the 
adjacent country, will admit of three parts in eight 
of nitrous air, before it is faturated. I mean, that if I 
put five parts of common air into the gage-tube, and add 
to it three parts of good nitrous air, the whole quajitity 
will diminifh to the original five j after this, as much 
nitrous air as is put into the tube, the column will appear 
jufl fo much longer. I commonly allow two minutes for 
its ftanding in the tube after fhaking it a little. 

H h 2 Air 

The appendix. 

Air which I have had brought to me in a bottle from 
one of the fick wards of our infirmary, has appeared 
to be about one fixth part noxious ; which is nearly 
the fame ftate as that brought from the bottom of a coal- 
pit in King's Wood, and air from a lead fmelting-houfe 
has been a third part noxious. 

The air brought from an eminence near this place, 
called Brandon Hill, has been found to be remarkably 
different, according to the weather and fituation of the 
wind. When the wind blows from the city, the air will 
not take fo much of the nitrous air to faturate it, as when 
it blows from the country. But to difcover the difference, 
proper attention muff be had to the ftate of the air in the 
room where the experiment is made. 1 am. 
Dear Sir, 

Your obliged humble fcrvant, 

J. B. Becket. 

N U M S E R V. 

J fecond Letter from Mr, BeckET to Dr. PriestleY, 
on the Subje£i of Air from Sea Water. 

Briftol, 24th Feb. 1779. 
Dear Sir^l 
I am vexed that I was not able to fend you any fea 
water to Calne. I had fome of it brought to me, Vv^hich, 
being taken up too near the fhore, was thick, and 1 fup- 
pofed, quite unfit for the purpofe : it was only a few da5'S 
ago that I was able to procure any that I could depend on. 
It was taken up about the middle of Caermsrthen Bay ; 
and the perfon who put it in the bottles told me, he clofed 


T H E A P P E N D I X. 46$ 

them up immediately. I proceeded with it in the fame 
manner that I informed you I did before with the Hot- well 
water, and have juft now finifhed the experiment. The 
refult was very nearly the fame as that from the Hot-well 
water, except that the fea water air was fomewhat more 
pure. The common air here, at this time, is exadlly in, 
the ftate which I have fixed as a ftandard with refped to 
the nitrous air; I mean, that five parts of common air 
take 3 parts of nitrous, and the whole appears as 5 j,« 
whereas the fea water took 4.25 of nitrous air before it was 
brought, to its original dimenfions, lam. 

Dear Sir, 

Very fincerely. 

Yours, &c. 

J. B. Becket, 


J Letter from Dr. DoBSOT^, «/" Liverpool, to Dr. Per^ 
ciVAL, ff/'Manchefter, on the Air from Sea-water. 

Liverpool, Jan. loth, 1779. 
I now fend you, my dear fir, the refult of the experi- 
ments on marine air, or the air procured from our fea water, 
by the heat of boiling water. 

Marine air put to the teft of nitrous air, was found 

to be one eighth of a meafur'e better than common air. 

The air; of Liverpool, tried by the fame nitrous air, was 

X5 of a meafure worfe than common air. — The air con- 

H h 3 tained 

470 T HE A P P E N D I X. 

talned in the bladders of our fea-weed, | of a meafurc 
worfe than common air. 

That the comparative difference of thefe three may nr.ore 
eafily a; d immediately be f en, I will fet them down in 
the manner I generally do in my experiments. — On my 
graduated tube, the interval between dephlogifticated air 
and perfectly noxious air, is divided into forty-two equal 
parts, and thus forms a fcale of forty-two degrees. — On 
this fcale, o is fixed at the divifinn which marks good 
common air. — From o up to dephlogifticated air, takes 
twenty two of thefe degrees ; and from o down to per- 
feftly noxious air, twenty -degrees. 

On adding one meafure of nitrous air to two meafure* 
of marine air, the mixture was fo much reduced in 
bulk, as to ftand at 2| degrees above o 
Liverpool air, flood at i degree below o 
Pod air, 4 degrees below o 

Marine air therefore is 2^ degrees better than good com- 
mon air. — The air of Liverpool, i degree worfe; and pod 
air, or the air from the bladders of our fea-weed, 4 degrees 
worfe. How it is, that the air contained in the bladders 
of our fea weed, (which were frefh gathered) Ihould 
differ from that examined by Dr. Prieftley, I cannot tell. 

The following was the method of procuring the air 
from fea water. — A quantity of clear rain water was firft 
boiled near four hours, fo as to be freed from its air. — Into 
this water,' when the heat was fuiEciently abated, was 
put a bottle containing three gallons of fea water ; and 
over the mouth of this bottle was inverted a cylindrical 
glafs receiver, the mouth of which refled on the fhoulder 
of the bottle. — After four hours, the heat of the boiling 
water had raifed about fix ounce meafures of air, or fome- 
thing more than zq ^^ ^^^ t)ulk of the fea water era- 

1 00* 


The appendix, 471, 

I obferved, that the efFervefcence, heat, and expanfion 
were much greater, and the fubfequent diminution much 
more rapid, on the mixture of marine air with nitrous air, 
than on the mixture of common air, or pod air, with 
nitrous air. — Marine air does not precipitate lime from 
lime water j and how far it is dephlogiflicated, hart)eea 
already mentioned. 

In making the above experiments I. was affiftedby Mr. 
William Rathbone, an ingenious young gentleman of this 

With aiFe£lion and efteem, 

I remain, 

Your's very fincerely, 

Mattk, Dobson. 

In a letter inclofing this. Dr. Percival fays, «' It will 
*' doubtlefs occur to your recollection that fea- water near 
*' Liverpool muft be mixed with impurities by the muddy 
*' frelh water of |the river Merley. The quercus marinus 
*' alfo, by growing on flimy banks will have its pods filled 
*' with worfe air than thofe which you obferved in an 
** open fea beach laft fummer. The feafon of ihe year 
" ihould likewife be adverted to." 


472 T H E A P P E N D I X. 


A Letter from Mr. Magellan, F. R. S. to Dr. 

Priestley, ov the Efficacy <?/" fixed Air for dljfolvlng the 
■' Stone, and in putrid Fevers^ tried in Holland. 

Dear Sir, 

Prince Gallitzin, the Rufli^n ainbaflador to the States 
of Holland, in a letter dated the 17th inftant informs mc 
of an extraordinary cure of a putrid fever by the internal 
application of fixed air, according to the method of Dr. 
Hulme, both in draughts and in elyflers ; and I have nov/ 
before me this cafe written by Dr. Janflens, an able phy- 

'iician of Operhout, near Breda, in the Dutch Brabant. 
The patient was a married woman, of thirty-two years old, 
whom he was called to attend on the ninth day by the af- 
fiftant phyfician, to be confulted, in an alarming circum- 
ftance, which the patient was already in, almofl: all covered 
with exanthems, of a red and livid colour, fhewing the 
greateft tendency to the laft llage of general putrefaction. 
All her limbs were in a ftate of flow convulfion, and par- 
ticularly with cold fweatings. The bark and all other 
means pointed out by medical art had been properly ap- 
plied, but without any fuccefs. Dr. JanfTens availed 

'himfelfof the hints he received in a converfation with 
Prince Gallitzin on the fubjecl, and ordered that the de- 
cofllon of the bark, till then inefFediual v/ith this patient, 
fliould be adminiftred mixed with the fait of tartar, 
and, vitriolic acid, both in draughts and elyflers, relying 
on the effeCl of the fixed air^ which was to be dif- 
engaged within the body of the patient. The fuccefs 
fully ar.fwered his expedations, for in three days time 
all bad fymptoms were over, and a perfcdl recovery was 
the confequence of this new treatment. Dr. Janflens 

' in 

The appendix. 473 

in this letter to Prince Gallltzin, fays, that although he 
confidered himfelf obliged to employ the quinquina (by 
the apprehenfion of a general putref iclion or gangrena, 
which he feared in To alarming a cafe) neverthelefs he be- 
lieved, that the fixed air had greatly contributed to this 

N. B. Prince Gallitzin in his faid letter, fubmits to 
farther confideration, whether the antifeptic virtues of the 
bark might not depend chiefly upon the large quantity of 
fixed air, it contains, as he has found by the analylis of 
this fubftance. 

1 apprehend the above information will be of fome fatis- 
faflion to yourfelf, and to every one who like yourfelf, 
has at the heart, whatever is good to mankind, 

I am with the greateft regard. 

And trueft afFeftion, 

Dear Sir, Your moft obed. humb. fervt. 

London, 27 February — 79. J. H. Magellan, 


474 T H E A P P E N D I X i 


A Letter from Dr. Ingenhousz, F. R. S. to Dr. 
Priestley, on theEffeSl of a new Species vf infammahU 
Air or Vapour, 

Dear Sir, 

As you found, that inflammable air becomes power- 
fully explofive by being mixed with a certain proportion 
of dephlogifticated air, I will give you a fhort account of 
an expeditious method to procure at pleafure any quan- 
tity of an inflammable air with very little trouble and a 
fimple apparatus, which I found out in the beginning of 
lafl: year, and which afforded me and my friends, to whom 
I communicated this difcovery, fome fatisfacStion. You 
were one of thofe, who took delight in feeing the experi- 
ment, which I had the pleafure of fhowing to you. 

Mr. Volta contrived fome kind of piftols, by which he 
could throw a leaden bullet to a confiderable diflance, by 
loading them with inflammable air mixed with common 
or dephlogifticated air. The force, w^ith which the bullet 
was propelled, and the loud report accompanying the ex- 
plofion made him believe, that this air might perhaps be- 
come a fubftitute for gunpowder. 

I was not far from believing, that his expeflation was 
well grounded ; but after having confidered the matter^ 
more maturely, I have altered my opinion, and think now, 
that the power of inflammable air, though great indeed, 
will afFord very little more than an amufing experiment, 
to be performed in the apartments of philofophers. I 
have communicated to you my confiderations upon that 
fubjesSl, and therefore will not take up your time in placing 
them in this lettter, efpecially as I intend to lay them be- 
fore the Royal Society. 


The appendix. 


If Mr. Volta's expedation of fubftituting inflammable 
air for gunpowder had been well grounded, the greateft 
defideratum^ I think, would have been to find outaneafy 
and ready method to procure fuch explofive air in any re- 
quired quantity, or to carry about fuch air ready made, 
in a concentrated ftate, fo as to occupy as little fpace as 
poflible, and to be always in readinefs for immediate ufe. 

I have perhaps fulfilled thefe conditions as near as pof- 
Hble ; for all the inflammable air neceflary for a piflol fuch 
as Mr. Volta contrived, is contained in the fpace of one 
lingle drop of a liquid. So that a pint bottle may contain as 
much inflammable air exifl:ing, as it were, in a concentrated 
ftate, as is required to fire an air piftol many thoufand 

This liquid is Vitriolic ather, the moft volatile of all 
liquids yet knov/n. 

An experiment, which I faw at Amfterdam, in Nov. 
1777, fuggefted to me this idea. Mr. Enee, a learned 
gentleman of that city, fhowed me fome experiments 
v/ith various inflammable airs : in one, he extra6ted a very 
powerful inflammable air from equal quantities of oil of 
vitriol and fpirit of wine, by applying heat to the phial 
containing thefe ingredients. One fourteenth of this air 
mixed with common or dephlogifticated air made a very 
loud report, when fired by an electrical explofion from a 
Leyden phial, and propelled a leaden ball with a very great 

I thought immediately, that the trouble of extra£l:ing 
this air in the way mentioned, might be difpenfed with, 
if fome drops of good aether were poured into the veffel in 
which it is to be fired. I propofed to try whether my 
idea was well founded, as foon as I fhould arrive in 
London, where I propofed to make fome ftay, to fee my 
old friends, and to acquire what new knowledge I could 
in medical and philofophical matters. 


476 The A P P E N D I X. 

Being arrived in this capital in the beginning of Jan. 
1778, I immediately fet about to try the experiment. I 
poured into a flrong glafs tube fome drops of sether, and 
diredted an ele£lrical fpark from a charged vial through 
jt ; but to my mortification the inflammable air difen- 
gaged from the aether did not kindle. I repeated the ex- 
periment in various ways, as for inftance throv^ing into 
the tube a bit of cotton dipped in asther, &c. but all to 
no purpofe. Hovi^ever I was much perfuaded in my own 
mind that the experiment muft fuccced in fome way 
or other, that the firfl failing could not difcourage me; 
and indeed 1 fuccecded once or tv/ice before the end of 
January, by throwing into the tube a bit of paper dipped 
in aether. Convinced now that I was right 1 purfued the 
experiment ; but did not venture to {how it to my friends 
till I had hit upon a method of fucceeding without fear of 
failing. I communicated early in the fpring ^my having 
difcovered a method of producing an iijflammable air at 
pleafure with a very fimple apparatus, to Sir JohnPringle, 
Prefident to the Royal Society, to Mr, Nairne and Blunt, 
and fome others of my friends, but did not procure 
this air before my friends in any other method than that 
I faw at Amilerdam. But foon after I began to fhow it 
to a few perfons, and fmce I have divulged it without 
fcruple. I found, that the reafon why I did not fucceed 
in my firft attempt, was, that I always poured in too grealj 
a quantity of aether, by which the inflammable air (or 
rather inflammable vapour, as it is capable of being ab- 
forbed by water) was not fufficiently diluted, which is a 
property common to all inflammable airs. 

1 find that onefingle drop of this liquid, poured into an 
inflammable air piftol, containing about ten cubic inches. 
Would communicate to the air within it a very ftrong ex- 
plofive force. 


The appendix. 


The moft expeditious and fureft method I hit upon, 
was to plunge the extremity of a fmall glafs tube (whofe 
bore was about two lines in diameter) into the aether, 
till 3 or 4 drops entered into the bore, then to fhut the 
upper end of the tulje, by applying my finger to it. 
Thus the little quantity of jether, which has entered the 
tube, will remain fufpended in it, and may be conveyed 
out of the bottle. I put this tube containing the aether 
immediately into a fmall caoutchouk, or elaftic gum bottle; 
then I withdraw my finger from the upper extremity of 
the tube ; and after having taken the tube out of the elaftic 
gum bottle, I thruft^ the orifice of this bottle into the bar- 
rel of the air piftol, and after giving it a gentle fqueeze, I 
withdraw it, and put a bullet or a cork into the mouth of 
the barrel of the piftol, v/hen it is ready to be fired by 
direding aneledlrical explofion from a fmall Leyden phial 
through it. 

It is to be obferved, that this inflammable air being 
heavier than common air will fettle to the bottom of the 
piftol, and thus eafily mifs catching flame from the 
fpark, if the piftol is not (hook, before the Leyden phial is 
applied to it. This air poftefles fome of the remarkable 
properties of the other inflammable airs, viz. it 
eatches flame only where it is in contail with common 
air, if the air be unmixed, it will not eafily inflame j and, if 
it does, it will burn quietly without exploding. It is un- 
fit for refpiration, and kills an animal plunged in it al- 
moft inftantaneoufly ; though it perfumes the common 
air with an agreeable fmell, and feems far from beij^g 
hurtful to the lungs in fuch a diluted ftate. 

If a fmall quantity of camphor is difiblved in the asther, 
the explofive force feems to be rather increafed. 1 have 
alfo tried it by difiblving a fmall quantity of phofphorus 
of Kunkel in it, and found it anfwer very well j but this 
laft compofition fhould not be poured ijito the piftol itfelf, 
' as 

478 The A P P E N D I X. 

as the phofphoric acid adhering to the inner furface of the 
piftol, foon attracts a coat of moifture, covering the 
whole cavity of the piftol, by which it v/ill foon mifs 
taking fire. Upon the whole, this laft compofition, 
though very brifk in taking fire, is apt to fail, after the 
experiment has been repeated fome times, which is occa- 
fioned, 1 fancy, by the moifture it communicates to the 

This inflammable air being much heavier than common 
air, does not fo eafily efcape out of the piftol as inflam- 
mable air extracted from metals by the vitriolic acid, if 
the orifice of the piftol is kept upright and open. 

It requires a ftronger electrical fpark than the other in- 
flammable airs, and can fcarcely be kindled with cer- 
tainty without a coated phial, which however may be very 
fmall, fothat one fquare inch of coating will be fufficient. 
It was well known before, that all fpirituous inflammable 
liquors have an inflammable atmofphere about them, prin^ 
cipally when heated, by which they are fometimes fet on 
fire, when the flame of a candle is imprudently brought too 
near them. But I think nobody employed this air, in 
which aether is decompofed, for the purpofe now men- 
tioned, before I communicated it to my acquaintances. 

It feems fomewhat remarkable, that though sether being 
in a liquid ftate does fo eafily evaporate, that fcarce any 
glafs ftopper can confine its extreme volatility ; yet the 
air, vapour, or elaftic fluid generated by it, is fo far from 
teing of a fimilar volatility, that it will remain even for 
hours together in an open glafs, without evaporating or 
mixing with the common atmofphere, or lofing its inflam- 
mable quality, which is to be afcribed to the fpecific gra- 
vity of this air being greater than that of common air. 

As I make no doubt but this air is the fame that might 
be extracted from oil of vitriol and fpirit of wine by heat, I 
will give you the following account of the fpecific gravity 


The appendix. 479 

of different inflammable airs compared with common air, . 
with which account I was favoured by Mr. Enee : 

A veflel containing common air to the weight of 138 
grains, will contain of inflammable air extradled from 
iron 25 grains ; of air extracted from marflies, 92 grains ; 
and of that extracted from oil of vitriol and fpirit of wine, 
150 grains, I am, 

Dear Sir, 

Yours, &c. 
jft March, 1779.' J. Ingenhou5Z. 


further Experiments on Pyrophori, in a Letter to tbfi 
Reverend Dr. Priestley ; By William Bewly. 

In my former paper on the fubjefl of Pyrophori, printed 
in the appendix to the 3d volume of your Ohfervations on 
Mr, 1 fuggefted objedlions againft the generally received 
hypothecs relating to the accenfion of the various clafles 
oi Pyrophori difcovered by Homberg and M. du Suvigny ; 
and which may properly enough be diftinguifhed by the 
titles of I. the Aluminous, or that of the Homberg ; 2. the 
Metallic, or thofe made with the three vitriols of iron, 
copper, zinc ; and 3. the Neutral, or thofe compofed of 
vitriolated tartar and Glauber's fait. Thp two laft clafles 
were difcovered by M. du Suvigny, who afcribed the 
fpontaneous accenfion of all the three kinds to the pre- 
fence of a highly concentrated vitriolic acid, exifting in 
them in an uncombined or nearly difeiigaged ftate, and 

\ generating 


generating a heat fufficlent to kindle the inflammable in- 
gredient, by eagerly attracting moifture from the air. 

In oppofition to this theory, in my letter above referred 
to, I afferted thzt Pyrophori of all the above-mentioned 
claffes might be prepared, which did not contain any vi- 
triolic acid ; and that therefore the caufe of the accenfion 
afligned by M. du Suvigny could not be the true one. I 
promifed likewife to take an opportunity of defcribing the 
proceffes on which this afTertion was founded. Though 
I have fince had reafon to fufpe6t that my general propo- 
fition might perhaps require fome modification, with re- 
fpe£t to one of the above-mentioned clafles of Pyrophori ; 
this cijcumftance by no means afFeds my aflertion re- 
fpedling the infufficiency of M. du Suvlgny's theory. I 
am forry that your work is in fuch forwardnefs at the 
prefs, as to allow me time only to relate a few of my ex- 
periments on this fubjeft, and on others nearly connected 
,with it; particularly thofe refpeding the hypothefis fug- 
gefted by myfelf. I fhall begin with thofe relating to 
what 1 have above called the Neutral F-n'ophorus, or that 
which M. du Svvieny prepared by fubflituting Glauber's 
fah, or vitnolated tartar, in the room of alum. The 
experiments immediately following, in which, for the 
fake , of brevity, I fhall confine myfelf to the Pyropbo- 
rw5 made with vitriolated tartar, will (liew that the. pre- 
fence of vitriolic acid is not necelTary to conilitutea Pjro- 
-pb'ortts of this fpeciss ; and would alone be fufficien-f, 
from analogy, to render it doubtful whether the other 
two claffes owe their accenfion to the agency of that 

I. To a quantity of vitriolated tartar, I added more 
than an equal weight of powdered charcoal, and calcijied 
the mixture a long time, in a red heat, in an open cru- 
cible ; frequently flirring the powder, in order tOiiexpel 
from it as much of the vitriolic acid as poffible. I have 


The appendix. 481 

fometlmes repeated the calcination with frefh charcoal. 
Neverthelefs, on treating the fait, thus^deprivcd of a con- 
iiderable part of its acid, with charcoal, in a crucible or 
tobacco pipe (in the manner defcribed in my former paper) 
I obferved no diminution in its quality of producing a 

2. Adding fucceffively various and increafing quantities 
of fixed aicali to the fait treated as above, till the vitriolic 
acid contained in the mixture might be confidered nearly 
as an evanefcent quantity ; a pyrophorus was ftill produced, 
on calcining it with charcoal as before. 

3. I mixed equal parts oi fait of tartar^ and vegetable or 
animal coal, or fometimes three parts of the former with 
two of the latter, and calcined them in the ufual manner. 
This compofition, on being expofed to the air generally 
kindled in the fpace of half a minute, or a minute. It did 
not burn with fo much vivacity as the vitriolic pyrophori, 
as it contained no fulphur. I fliall hereafter denominate 
this the Jlcaline pyrophorus. It differs in no one cir- 
cumftance from M. du Suvigny's Neutral pyrophori, ex- 
cept in its not containing that very principle to which he 
afcribes their accenfion. 

4. It will perhaps be thought a remarkable cir-cum- 
ftance, on which I cannot now, however, dwell particu- 
larly, that the coal of blood, after all its colouring, or 
phlogijlic matter (as it is called) had been exhaufted, fo 
that it would no longer furnifh an atom of Pruffian blue, 
appeared to be'better adapted than before to the producing 
a pyrophorus. 

5. Left it might be fufpe£ted that the fait of tartar 
«vhich I employed might accidentally contain vitriolated 
tartar, or vitriolic acid; I repeated the experiment with 
tartar calcined by myfelf, as well as with nitre fixed or 
alcalifed by deflagration with charcoal, and with. iron 
filings : but in all thefe cafes the event was the fame. 
It is rather furprifing that this alcalint pyrophorus fliouM 
not have been difcovered before j as I have more than 

1 i once. 

482 The A P P E N D I X* 

once, fince I firft obferved it, on preparing the Prujftsn 
alcall, feen the lower part of it take fire, foon after its 
having been turned out of the crucible, and bruifed j even 
when the matter had not been covered v^ith fand. 

For the fake of thofe who may be inclined to repeat 
this experiment, I fhould obferve that there is fomething 
capricious in the procefs. It has fucceeded five or fix 
times fucoeffively, and has fometimes failed as often ; 
though in both cafes, I ufed a mixture of alcali and char- 
coal taken out of the fame phial. I know not yet the 
circumftance on which this variety in the refults depends : 
though I rather apprehend that a ftronger heat is necef- 
fary than when vitriolic acid is contained in the falinc 

Expecting fimilar refults from diverfifying, in a fimilar 
manner, M. du Suvigny's experiments on the metallU 
pyrophori, I foon found that none of the three vitriols, 
heated with charcoal ^lone, in my ufual manner, would 
produce a pyrophorus. I recollefted that he conftantly 
added an akaline fait to the compofition ; though I be- 
lieve he no where obferves that this additien is eflentially 
necefiary to the fuccefs of the procefs, as will appear frorai 
the following experiments made with the green vitriol. 

y. Treating in the ufiial manner equal parts of calcined 
green vitriol and charcoal, the powder did not acquire any 
of the properties of a pyrophorus. It contained no ful- 
phur, nor hepar fulphuris. In fliort, the vitriolic acid 
, feemed to have been intirely diflipated ; having no bafe to 
detain it, when diflodged from the metallic earth : this 
laft not appearing to be adapted, like that of alum, to form 
a hepar fulphuris with fulphur; although fome chemifta 
have confidered the metallic and aluminous earths as being 
nearly lelatead.^ 

8. The charcoal and calx of iron, left in the laft pro- 
cefs, were calcined again, together with fome fait of tar- 
tar added to the compofition. A pyrophorus was pro^ 
ducedj which, on examinatipn, exhibited indications of 



i^S containing a fcarce perceptible portion oi hepar fulphu' 
tisy undoubtedly formed in confequence offomefmall part 
of the green vitriol having efcaped decompofition in the 
preceding procefs. 

9. Thirty grains o( Crocus Al^trtis ajlnngens were Calcined 
with 15 grains of charcoal and the fame quantity of fait 
iof tartar. This mixture likewife burnt fpontaneoufly ; 
though it contained no hepar fulphurisy or vitriolic acid. 

Thefe experiments (§ 7. ^, 9.) afcertain the truth of 
my aflertion w^ith refpe£l to this clafs likewife of M. du 
Suvigny's pyrophori. The aluminous only remains. My 
ipropofition, fo far as relates to it, was founded on the 
following experiment. 

10. I procured the earth of aliim by a long and violent 
calcination ; ufmg double the quantity of inflammable; 
inatter direSed by Beaume. Examining a part of it, I found 
by theufual tefls, that it neither contained any fujphur, he- 
par fulphuris, or alum undecompounded. I therefore 
confidered it as perfectly pure. It repeatedly furniftied ^ 
pyrophorus, as active as when alum itfelf is employed. 

I u I have fmce found, however, that this fuppbfed purQ 
earth contained a fmall quantity of vitriolated tartar. 
Having walhed the earth, which I had negleded to do 
before, a pyrophorus was npt produced in two Or three 
trials made with it. I have likewife Failed when I have 
employed this earth precipitated by an alcali ; and yet the 
quantity of vitriolic acid leftan the earth (§ 10.) was verv 
incohfiderable. I am forry I have not had an oppor- 
tunity to invelligate the caufe of th\'s feemlng exceptioa 
to my general propofition. 

The infufficiency of M. du Suvigny's theory appears, 
ijeverllielefs, evident from thefe experiments. Even allow- 
ing the vitriolic pyi-ophori (or thofe which contain vitriolic 
acid) to be kindled merely by their attrafting moifture 
from the atmofphere j the earthy or faline hcpar fulphu- 
r'lSy which is confiantly formed in the procefs, muft be 
the ingredient that attraipfs this humidity j and not a fup- 

I i 2; pofed 

484 The APPENDIX. 

pofed glacial vitriolic acid, which, in an uncomhlned^ or 
even loofely combined ftate, muft have been foon diffipated 
in a ftrong red heat j to which, fometimes rifing even to 
a white heat, I have expofed thefe pyrophori four hours, 
not indeed without a fenfible lofs of bulic, but with no 
perceptible diminution of their pyrophoric quality. 

12. Some of your experiments contained in this vo- 
lume feem ftrongly to favour the hypothefis I former- 
ly fuggefted, and to (hew that moifture is not the 
fole caufe, at leaft, of the accenfion of pyrophori ; as they 
are kindled in dry nitrous and dephlogifticated air f . I 
calcined the ingredients of my alcaJine^yrophorviSy fepa- 
rately, in a ftrong heat j mixing with the alcali fome 
black lead, iron filings, and other matters not inflam- 
mable, to prevent fufion or vitrification. The fait did 
not grow warm on breathing upon it, and imparted only 
a flight warmth to my hand previoufly moiftened. Itjiiil 
sontinued mild. No warmth was produced on mixing it 
with the charcoal from the other pipe, or with fome moift 
charcoal, or fulphur. 

13. I muft obferve, however, that on calcining the al- 
caline fait with twice its weight of the calx of PruJJian 
Hue deprived of all its colouring matter by repeated digeftions 
in alcaline lixivia, the refults were fomewhat different. 
The mixture did not indeed grow warm on breathing 
upon it, or on mixing the charcoal with it ; but it became 
pretty hot on adding a little water to it. The alcali was he- 
comi perfeSlly caujiic. It had likewife difTolved a confiderablc 
quantity of the aluminous earth. A folutionof it exhibited 
a kind oi liquor ftlicum. A little fpirit of vitriol added pre- 
cipitated the earth. Neutralifing the liquor, the earth 
was inftantly rediflblved, and the liquor was ftrongly alu- 
mi nous : an alcali added again precipitated the earth. 

14. In 
See page 64, and 259 of the prcfent volume t The inftantane- 
ous accenfion of the pyrophorus in thefe two inftances cannot be 
afcribed to the fmall portion of phlegm, that can reafonably be fup- 
pofed to be contained in the nitrous and dephlogifticated air, which 
was thrown up into fmall jars, ufed in thefe experiments. 

The appendix. 485 

14. In the alcaline pyrophorus, fome kind of combina- 
tion feems to be formed between the alcali and fome prin- 
ciple in the coal. On the firft degree of warmth produced 
on breathing upon it, a faint phlogiftic fmell is perceived. 
Acids added to a fol-ation of it precipitate a fmall quantity 
of a fubftance that does not feem to be the mere coal dif- 
folved by the alcali, but a kind of fulphur, which, how- 
ever, does not kindle fo readily as vitrioUe fulphur, and 
which leaves fome afties, probably the earth of the coal. 

In a curious paper on pyrophori, publiflied by M. Proti/f, 
in the Journal de Medecine for July laft, with a copy of 
which I have been favoured by the ingenious author; 
after reciting fome of my experiments, and concurring 
with me in rejecting iVl, du Suvigny's theory, he briefly 
defcribes a variety of new pyrophori, which neither con- 
tain vitriolic acid; or feem likely to owe their accenfion to 
the attra^lipn of humidity from the air. They prin- 
cipally confift of a coaley matter fimply divided by me- 
tallic or other earths. Such are the fediment l^h on the 
filtre in preparing Goulard^s extraSf, various combina- 
tions of tartar, or its acid, or the acetous acid, with 
metals, calcareous earth, ^c. M. Prouft allerts like- 
wife the detonation of charcoal, firft ignited and fufFered 
to cool, with nitrous acid j an experiment which did 
not formerly fucceed with me, probably on account of 
the weaknefs of the acid I employed. It is to be hoped 
that he will favour us with a more particular detail of his 
very interefting experiments, which cannot fail to throw 
confiderable light on this fubjedt. It may, perhaps, 
be further illuftrated by attending to the Abbe Fontana's 
late curious difcovery, relative to the fingular property 
which charcoal, previoufly heated, poflefTes of attracting 
and abforbiiig great quantities of air, while it is cooling. 
Great Maflingham, I am, &c, 

March 6, r779. Wm, Bewi-y, 

C 4S6 3 

"Remarks on fome Parts of this Volume. 

HAVING, in fome parts of this volume, ventured 
to launch beyond the bounds of the do£lrine con- 
cefning air into the region of a more extenfive chemiftry,, 
jjl w^hich I profefs myfelf to be but a novice, and being un- 
willing to advance any trite obfervations as difcoveries of 
my own, and more efpecially fearful of having fallen intp 
fome miftakes, Ibegged the favour of my chemical friends, 
Mr. Bev/ly, JVlr. Keir, and Mr. Hey, to perufe the work 
when it was printed off, and to coipmunicate fuch ob- 
fervations as might enable me to make it, in any refpe<S, 
more corredl than I was able to do it myfelf. Ac- 
cordingly they were all fo obliging as to go over the Vv'hole 
with that view, and the following are the remarks for 
which my readers and myfelf are indebted to their friend- 
ship; as well as for^ fome of the corre6lions inferted in 
the errata^ 

'' P. 19. 1. 5. '■^ I doubt whether the ftrength of nitrous 
** acid can be afcertained by the quantity of nitrous air 
*' which it produces during a folution of copper, as I 
" think a phlogifticated acid would produce more air 
«' than an unphlogiilicated acid would, of equal ftrength. 
" Perhaps the ftrength of acids is beft afcertained by the;r 
" denfity," Mr, Keir. 

P. 64 and 259. I have called the preparation defcrlbed 
in the Appendix to my third Volume, p. 402, by the name 
of Mr, Bewlfspyrophorus. But the pyrophorus which 


[ 487 ] 

is properly his is only announced in general terms in that 
Appendix, and is defcribed at large in the Appendix to 
the prefent Volume. 

P. 86. 1. 10. The difcovery of the power of the 
marine acid to diflblve earthy fubftances has been long 
known to chemifts, as I have myfelf obferved in the pre- 
ceding page 1. 20. I ought therefore to have exprefled 
myfelf in fome fuch manner as this, Having obferved the 
effeSl of the folution of earths in the marine acid, I was, &c. 
P. 91. 1. 19. " Some of the fubftances here mentioned 
** are generally believed to be ailed upon by the marine 
" acid, and pretty explicit experiments would be r^quifite to 
** prove that, notwithftanding all the'proper attention had 
*' been paid to heat, time, pounding of the materials, 
*' different ftrength of the acid, and other ufual circum- 
*' ftances, this acid was incapable of acting upon thefe 
?' fubftances. Zeolyte is faid to be foluble in acids in 
f* general. The alkaline bafis of cream of tartar has been 
•' feparated by the vitriolic and nitrous acids, and it would 
f« be remarkable if it could not be by the marine acid, 
f* Borax is generally faid to be capable of being de-. 
** compofed by all, even the vegetable acid. The adtion 
♦.' of acids on none of thefe fubftances is accompanied 
*' with eff^ervefcence." Mr. Keir. 

N. B. Obferving no eft'ervefcence, or change of colour 
in the acid, there was no fuch effeil as I was looking for ; 
but I exprefled myfelf too generally in faying there was no 
fenfible, effpft at ^U. 

P. 107. Common fait contains a portloji of a fait con- 
fifting of the marine acid united with an earthy bafis. By 
boiling, the acid efcapes, and the earthy matter makes the 
liquor cloudy, and 'depofits an incruftation. The fame 
appearance is obferved in boiling dov/n fea water to nlak* 
(alt. Mr. Keir, 

I i 4 P. 122. 

[ 488 3 

P. 122. SeiStion XIV. I by no means meant to in- 
finuate that the convertibility of the volatile vitriolic acid 
into the common vitriolic acid v^as a difcovery of mine ; 
but only that the fa^s here recited are new proofs of it, 
or rather fa^s worth notice independent of that objedl:* 

P. 234. 1. 5. (b) Jlmoft all the mercury zVloft. *' You 
*' mean only that the mercury continues in the^ftate of a 
" calx, or a fublimate. But Mr, Bayen revived 4 
** drachms and 15 grains from an ounce of turbith mi- 
^' neral, without charcoal or other addition. Rozier torn 6. 
** part 2. Dec. 1775, p. 490." Mr. Bewly. 

P. 392. 1. 12. Common pit-coal yields no fixed air. ** I 
*^ remember to have obtained a great deal of fixed air, 
'^ mixed with inflammable air, from the pit-coal I tried, 
*' which was that of Stourbridge." Mr, Keir. 

P. 404. 1. 8. I obferve that the cream of tartar appear- 
ed, from this experiment, to be of the nature of vegetable 
matter. Dr. Hales, as Mr. Keir reminds me, obtained 
from tartar one third of its weight of air, and that, in his 
own Treatife on Gafes, he has obferved that the air ob- 
tained from it was a mixture of fixed and inflammable air, 

P. 413. 1. 16. " Mr. Rouelle has fliewn that water 
?' impregnated with fixed air does dilTolve calx'es of iron, 
** See Lavoifier's Opufcules." Mr. Keir. 

P., 419. 1. 18. " The heat would as foon decompofe 
*' and blacken the oil itfelf, as it would a ftraw : for 
*' v/hen ftraws, &c. are blackened by heat, it is in confe- 
?* fequence of the decompofition of the oil which they 
5* contain?" Mr, Keir, 


I 489 J 


I. Of the Effea 9f Light on Water. 
Y obfervation that light difpofes water, containing 


calcarious and other fubftances, to make a depofit 
of a greenifli or brownifh matter, and then to yield de- 
phlogifticated air, feems to be confirmed by the following 

On the 19th of Feb. 1779, I placed two jars of pump 
water, each containing about 170 ounces, in the fame 
• fouth window, one of them nearly covered from the fun 
with brown paper, and the other quite uncovered. In 
about ten days the water in the uncovered jar had yielded 
about four ounce meafures of air, and the covered jar only 
a few bubbles. Taking a journey I could make no farther 
obfervations on thefe jars till my return j but on the fecond 
of April I found that the uncovered jar had yielded ten 
ounce meafures of air, fo pure that one meafure of it and 
one of nitrous air, occupied the fpace of .84 meafures ; 
whereas the covered jar had very little more than one 
ounce meafure, and with this the meafures of the teft were 
1.55 meafures ; i. e.hy no means fo pure as the former. 
Alfo the uncovered jar had a fediment larger than the 
other in about the fame proportion, vi%. of ten to one. 
Oil of vitriol expelled from this fediment a very great 
quantity of fixed air. N. B. The loweft part of the jar was 
not covered with th^ paper, left being moiftened with 
the water, in the difh in which the jar ftood inverted, 
it (hould imbibe the water, and caufe it to evaporate too 

2. Of the Solution of Copper in the Sand Heat, 

The faline fubftance formed by the union of copper and 
fpirit of nitre is faid to be extremely deliquefcent, but that 
which is mentioned p. 415, 1, 6. I find not to deliquefcc 


[ 490 I 

at all. As thisfeems to be a new chemical preparation, and 
is eafily made, it may perhaps be of fome ufe, as a cauftic, 
or otherwife. It may be worth while to examine this fub- 
ftance, and alfo that from mercury in other refpe6ts, and 
to extend the procefs to other metallic fubftances. 

3. Of Sulphur from vitriolic Acid Air, 

The produdtion of real fulphur from water impregnated 
with vitriolic acid air may perhaps help to explain the rela- 
tion that fulphur bears to water, and decide the difputes 
about the prefence of fulphur in fome mineral waters. 

I would farther obferve, that the vitriolic acid air with 
which the water, in the experiment here referred to, was 
impregnated, was made from a «z^/^/, viz. copper. This 
circumftance Mr. Bewly thinks renders the fa6t more curi- 
ous ; as affording an additional and ftriking proof of the 
ftriiSl identity of the inflammable principle in metals^ and 
in oils and other inflammable fubflances. 

4. Of Cures effeSied hy fixed Air, 

1 have received from Mr. Magellan a fecond letter, 
which I cannot conveniently infert, containing an ac- 
count of a quartan ague (the confequence of a bilious com- 
plaint) being cured by the ufe of fixed air, in Dr. Hulme's 
method j and what is more remarkable ftill, a cure of a 
dropfy^ after all other remedies had failed, and the patient 
had been tapped five times. 

The phyfician who made thefe fuccefsful prefcriptions 
was Dr. Coopmans of Franeker in Frezeland, and the 
account was tranfmitted to Mr. Magellan from Princ^ 
Gallitzcn at the Hague. 

The more confiderable ERR ATA oftheprefs, and other corre^ion$, 
N. B. (^) means from the bottom, 

Introduftion, p. 29. I. 13. for fig. 3. read fig. 4. 
page. 2. 1. 3 {h) for more, read mere. 










13. andp.24-6. l.g.for hundred YCzA hundredth. 

2. 3. read to the mercury from the nuater. 
9. read mercury in ivater. 
1 (b) for nolivithfanding rezd and. 
6. for dephlogificatedrea.dphlogi/}icated. 
9. for it read an ounce of it, 

3. 4 (b) dele on <which the n)itriolic acidhas no proper aiiion*. 
6. 8. for nitre re^A ochre. 
6 . for a pound read an ounce. 
6. (b) foi' having read leaguing. 
6. read may be oiving, in fame meafure, 
I (^b") Tf3.A^as 'worked a full half hour* 
9. read North Eaft. 

5. (b) for phlogijlicated rf&dphlogijion, 
I. (^b) for /^jr^"^ read t'^vo. 
8. read //"^z/ it is of the nature. 
16. {b) for exanthems read exanthemata* 
8. (^) for /Af Jiomhergrt2L<S.Homberg, 

6. for Z2/2C read aw^ z/wr. 

7. for agency rt^d prefence or agency, 

ERRATA of Icfs confequcnep. 

page 9. 1. 4. for did read I did. 








and 367. 1. 7. d&\tand, 

3. for vjas read is. 

8. and 47. 1. 5. (b) dele//. 
2 (^b) for the read in the. 
8. for efaped read efcaped. 
1 5 . for hypothejis read hypothefes, 
1 2 . for A«(^ read ouflj. 

12. for Jortis read Fortis. 

4. read tubes filled •ivith inflammable «ir» 
19. for 'ventulated rezd-ventilated, 

10. for /Z'^/ read ^/^(^^ /^f, 
19, for //;<? read that the. 
3. for the pan read a pan. 
I ('/'^ for ^ir read /^^ «2>. 

1 3 . read ijifiam?nable air. 
15. for lay read lie. 

5 (^) read thefa?ne appearances. 
6. (^) read ««^ %inc. 





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